Add front matter to index.css

Added YAML front matter delimiters at the top of index.css, possibly for integration with a static site generator or build tool that requires front matter in CSS files.

Author: PeterMaZep

assets/css/index.css

@@ -1,3 +1,5 @@
+---
+---
 /* About Section */
 .about-section h2 {
     font-size: 2rem;