style: import Rubik font and update CSS variables for improved typography and consistency

- Added Rubik font from Google Fonts as the primary font family.
- Corrected CSS variable syntax for color definitions.
- Ensured consistent formatting for dark mode color variables.

Author: tyler-dane

src/css/custom.css

@@ -4,27 +4,38 @@
  * work well for content-centric websites.
  */
 
+/* Import Rubik font from Google Fonts */
+@import url("https://fonts.googleapis.com/css2?family=Rubik:ital,wght@0,300;0,400;0,500;0,600;0,700;0,800;0,900;1,300;1,400;1,500;1,600;1,700;1,800;1,900&display=swap");
+
 /* You can override the default Infima variables here. */
 :root {
   --ifm-color-primary: #005b94;
-  --ifm-color-primary-dark: #005285	;
-  --ifm-color-primary-darker:#004d7e	
-  --ifm-color-primary-darkest: #004068	
-  --ifm-color-primary-light:#0064a3 
-  --ifm-color-primary-lighter: #0069aa
-  --ifm-color-primary-lightest: ##0076c0	
+  --ifm-color-primary-dark: #005285;
+  --ifm-color-primary-darker: #004d7e;
+  --ifm-color-primary-darkest: #004068;
+  --ifm-color-primary-light: #0064a3;
+  --ifm-color-primary-lighter: #0069aa;
+  --ifm-color-primary-lightest: #0076c0;
   --ifm-code-font-size: 95%;
   --docusaurus-highlighted-code-line-bg: rgba(0, 0, 0, 0.1);
+
+  /* Set Rubik as the primary font family */
+  --ifm-font-family-base: "Rubik", -apple-system, BlinkMacSystemFont, "Segoe UI",
+    "Roboto", "Oxygen", "Ubuntu", "Cantarell", "Fira Sans", "Droid Sans",
+    "Helvetica Neue", sans-serif;
+  --ifm-heading-font-family: "Rubik", -apple-system, BlinkMacSystemFont,
+    "Segoe UI", "Roboto", "Oxygen", "Ubuntu", "Cantarell", "Fira Sans",
+    "Droid Sans", "Helvetica Neue", sans-serif;
 }
 
 /* For readability concerns, you should choose a lighter palette in dark mode. */
-[data-theme='dark'] {
+[data-theme="dark"] {
   --ifm-color-primary: #48b5f9;
-  --ifm-color-primary-dark: #29a8f8	;
-  --ifm-color-primary-darker:#19a2f7	
-  --ifm-color-primary-darkest: #0789da	
-  --ifm-color-primary-light:#67c2fa 
-  --ifm-color-primary-lighter: #77c8fb
-  --ifm-color-primary-lightest: ##a5dbfc	
+  --ifm-color-primary-dark: #29a8f8;
+  --ifm-color-primary-darker: #19a2f7;
+  --ifm-color-primary-darkest: #0789da;
+  --ifm-color-primary-light: #67c2fa;
+  --ifm-color-primary-lighter: #77c8fb;
+  --ifm-color-primary-lightest: #a5dbfc;
   --docusaurus-highlighted-code-line-bg: rgba(0, 0, 0, 0.3);
 }