docs: Add small refinements to CSS adjacent pages (#31683)

Follow up to https://github.com/zed-industries/zed/pull/31681. Was
visiting some of these pages and noticed these somewhat small formatting
and copywriting improvement opportunities. The docs for Svelte in
particular felt somewhat unorganized.

Release Notes:

- N/A

docs/src/languages/css.md

@@ -1,18 +1,19 @@
 # CSS
 
-CSS support is available natively in Zed.
+Zed has built-in support for CSS.
 
 - Tree-sitter: [tree-sitter/tree-sitter-css](https://github.com/tree-sitter/tree-sitter-css)
 - Language Servers:
   - [microsoft/vscode-html-languageservice](https://github.com/microsoft/vscode-html-languageservice)
   - [tailwindcss-language-server](https://github.com/tailwindlabs/tailwindcss-intellisense)
 
-<!--
-TBD: Document CSS
-TBD: Document [Tailwind CSS](./tailwindcss.md)
--->
+## Tailwind CSS
 
-## See also:
+Zed also supports [Tailwind CSS](./tailwindcss.md) out-of-the-box for languages and frameworks like JavaScript, Astro, Svelte, and more.
+
+<!-- TBD: Document CS -->
+
+## Recommended Reading
 
 - [HTML](./html.md)
 - [TypeScript](./typescript.md)