docs: Fix language links (#26368)

This PR fixes some language links in the docs.

The Shell Script page wasn't being linked from `SUMMARY.md`, so no page
was being generated.

There were also some differences in the language lists in the sidebar
and on the top-level languages page.

Release Notes:

- N/A

docs/src/SUMMARY.md

@@ -115,6 +115,7 @@
 - [Rust](./languages/rust.md)
 - [Scala](./languages/scala.md)
 - [Scheme](./languages/scheme.md)
+- [Shell Script](./languages/sh.md)
 - [Svelte](./languages/svelte.md)
 - [Swift](./languages/swift.md)
 - [Tailwind CSS](./languages/tailwindcss.md)

docs/src/languages.md

@@ -28,6 +28,7 @@ Zed supports hundreds of programming languages and text formats. Some work out-o
 - [Go](./languages/go.md)
 - [Groovy](./languages/groovy.md)
 - [Haskell](./languages/haskell.md)
+- [Helm](./languages/helm.md)
 - [HTML](./languages/html.md)
 - [Java](./languages/java.md)
 - [JavaScript](./languages/javascript.md)
@@ -58,7 +59,7 @@ Zed supports hundreds of programming languages and text formats. Some work out-o
 - [Shell Script](./languages/sh.md)
 - [Svelte](./languages/svelte.md)
 - [Swift](./languages/swift.md)
-- [TailwindCSS](./languages/tailwindcss.md)
+- [Tailwind CSS](./languages/tailwindcss.md)
 - [Terraform](./languages/terraform.md)
 - [TOML](./languages/toml.md)
 - [TypeScript](./languages/typescript.md)