Skip newlines when parsing selectors

[RobinMalfait]

This PR introduces a small improvement when parsing CSS where selectors including newlines (\n) are replaced with a space.

This means that the preflight in Tailwind Play looked like this:

/*! tailwindcss v4.0.0-alpha.9 | MIT License | https://tailwindcss.com */
@layer base {
  *,
::after,
::before,
::backdrop,
::first-letter,
::file-selector-button {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
    border: 0 solid;
  }
  html,
:host {
    line-height: 1.5;
    -webkit-text-size-adjust: 100%;
    tab-size: 4;
    font-family: var( --default-font-family, ui-sans-serif, system-ui, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol', 'Noto Color Emoji' );
    font-feature-settings: var(--default-font-feature-settings, normal);
    font-variation-settings: var(--default-font-variation-settings, normal);
    -webkit-tap-highlight-color: transparent;
  }
  body {
    line-height: inherit;
  }
  hr {
    height: 0;
    color: inherit;
    border-top-width: 1px;
  }
  abbr:where([title]) {
    -webkit-text-decoration: underline dotted;
    text-decoration: underline dotted;
  }
  h1,
h2,
h3,
h4,
h5,
h6 {
    font-size: inherit;
    font-weight: inherit;
  }
  a {
    color: inherit;
    -webkit-text-decoration: inherit;
    text-decoration: inherit;
  }
  b,
strong {
    font-weight: bolder;
  }
  code,
kbd,
samp,
pre {
    font-family: var( --default-mono-font-family, ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, 'Liberation Mono', 'Courier New', monospace );
    font-feature-settings: var(--default-mono-font-feature-settings, normal);
    font-variation-settings: var(--default-mono-font-variation-settings, normal);
    font-size: 1em;
  }
  small {
    font-size: 80%;
  }
  sub,
sup {
    font-size: 75%;
    line-height: 0;
    position: relative;
    vertical-align: baseline;
  }
  sub {
    bottom: -0.25em;
  }
  sup {
    top: -0.5em;
  }
  table {
    text-indent: 0;
    border-color: inherit;
    border-collapse: collapse;
  }
  button,
input,
optgroup,
select,
textarea,
::file-selector-button {
    font: inherit;
    font-feature-settings: inherit;
    font-variation-settings: inherit;
    color: inherit;
    background: transparent;
  }
  input:where(:not([type='button'], [type='reset'], [type='submit'])),
select,
textarea {
    border: 1px solid;
  }
  button,
input:where([type='button'], [type='reset'], [type='submit']),
::file-selector-button {
    appearance: button;
  }
  :-moz-focusring {
    outline: auto;
  }
  :-moz-ui-invalid {
    box-shadow: none;
  }
  progress {
    vertical-align: baseline;
  }
  ::-webkit-inner-spin-button,
::-webkit-outer-spin-button {
    height: auto;
  }
  ::-webkit-search-decoration {
    -webkit-appearance: none;
  }
  summary {
    display: list-item;
  }
  ol,
ul,
menu {
    list-style: none;
  }
  textarea {
    resize: vertical;
  }
  ::placeholder {
    opacity: 1;
    color: color-mix(in srgb, currentColor 50%, transparent);
  }
  :disabled {
    cursor: default;
  }
  img,
svg,
video,
canvas,
audio,
iframe,
embed,
object {
    display: block;
    vertical-align: middle;
  }
  img,
video {
    max-width: 100%;
    height: auto;
  }
  [hidden] {
    display: none!important;
  }
}

Now looks like this:

/*! tailwindcss v4.0.0-alpha.9 | MIT License | https://tailwindcss.com */
@layer base {
  *, ::after, ::before, ::backdrop, ::first-letter, ::file-selector-button {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
    border: 0 solid;
  }
  html, :host {
    line-height: 1.5;
    -webkit-text-size-adjust: 100%;
    tab-size: 4;
    font-family: var( --default-font-family, ui-sans-serif, system-ui, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol', 'Noto Color Emoji' );
    font-feature-settings: var(--default-font-feature-settings, normal);
    font-variation-settings: var(--default-font-variation-settings, normal);
    -webkit-tap-highlight-color: transparent;
  }
  body {
    line-height: inherit;
  }
  hr {
    height: 0;
    color: inherit;
    border-top-width: 1px;
  }
  abbr:where([title]) {
    -webkit-text-decoration: underline dotted;
    text-decoration: underline dotted;
  }
  h1, h2, h3, h4, h5, h6 {
    font-size: inherit;
    font-weight: inherit;
  }
  a {
    color: inherit;
    -webkit-text-decoration: inherit;
    text-decoration: inherit;
  }
  b, strong {
    font-weight: bolder;
  }
  code, kbd, samp, pre {
    font-family: var( --default-mono-font-family, ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, 'Liberation Mono', 'Courier New', monospace );
    font-feature-settings: var(--default-mono-font-feature-settings, normal);
    font-variation-settings: var(--default-mono-font-variation-settings, normal);
    font-size: 1em;
  }
  small {
    font-size: 80%;
  }
  sub, sup {
    font-size: 75%;
    line-height: 0;
    position: relative;
    vertical-align: baseline;
  }
  sub {
    bottom: -0.25em;
  }
  sup {
    top: -0.5em;
  }
  table {
    text-indent: 0;
    border-color: inherit;
    border-collapse: collapse;
  }
  button, input, optgroup, select, textarea, ::file-selector-button {
    font: inherit;
    font-feature-settings: inherit;
    font-variation-settings: inherit;
    color: inherit;
    background: transparent;
  }
  input:where(:not([type='button'], [type='reset'], [type='submit'])), select, textarea {
    border: 1px solid;
  }
  button, input:where([type='button'], [type='reset'], [type='submit']), ::file-selector-button {
    appearance: button;
  }
  :-moz-focusring {
    outline: auto;
  }
  :-moz-ui-invalid {
    box-shadow: none;
  }
  progress {
    vertical-align: baseline;
  }
  ::-webkit-inner-spin-button, ::-webkit-outer-spin-button {
    height: auto;
  }
  ::-webkit-search-decoration {
    -webkit-appearance: none;
  }
  summary {
    display: list-item;
  }
  ol, ul, menu {
    list-style: none;
  }
  textarea {
    resize: vertical;
  }
  ::placeholder {
    opacity: 1;
    color: color-mix(in srgb, currentColor 50%, transparent);
  }
  :disabled {
    cursor: default;
  }
  img, svg, video, canvas, audio, iframe, embed, object {
    display: block;
    vertical-align: middle;
  }
  img, video {
    max-width: 100%;
    height: auto;
  }
  [hidden] {
    display: none!important;
  }
}