add lines and wrap-mode properties to label widget

[vaporii]

Description

Add the :lines and :wrap-mode properties to the label widget. Used for setting the number of lines to display when wrapping is enabled, and how it should display wrapped text, respectively.

Usage

To set the lines and wrap-mode properties, you could do something like this:

(label
  :text "this is some label text blah blkaghk kwjhndlkaj wbn akj hba jkhawbjakhjhawjkdbh jahbw ajkhbakjawja"
  :wrap true
  :limit-width 15
  :lines 4 ; the number of lines to display
  :wrap-mode "char" ; wraps on characters, ignoring words
)

This will look like the first image in the showcase below.

Showcase

Additional Notes

When the label text contains newlines, they aren't interpreted as lines. This fix involves changing the implementation of newlines in labels, or implementing some janky fix elsewhere

Checklist

• All widgets I've added are correctly documented.
• I added my changes to CHANGELOG.md, if appropriate.
• The documentation in the docs/content/main directory has been adjusted to reflect my changes.
• I used cargo fmt to automatically format all code before committing

[w-lfchen]

looks good overall, thank you for your work <3

[w-lfchen]

lgtm, thank you again <3