docs: update secondary action to contributing (#1969)

Author: uncenter

docs/src/content/docs/index.mdx

@@ -11,8 +11,8 @@ hero:
     - text: Get Started
       link: /getting-started/introduction
       icon: right-arrow
-    - text: Contribute on GitHub
-      link: https://github.com/catppuccin/userstyles
-      icon: external
-      variant: minimal
+    - text: Contribute
+      link: /contributing/
+      icon: right-arrow
+      variant: secondary
 ---