docs: Improve Haskell documentation (#27372)

Closes: https://github.com/zed-industries/zed/issues/27365

Release Notes:

- N/A

docs/src/languages/haskell.md

@@ -5,9 +5,32 @@ Haskell support is available through the [Haskell extension](https://github.com/
 - Tree-sitter: [tree-sitter-haskell](https://github.com/tree-sitter/tree-sitter-haskell)
 - Language Server: [haskell-language-server](https://github.com/haskell/haskell-language-server)
 
-See: official [configuring haskell-language-server](https://haskell-language-server.readthedocs.io/en/latest/configuration.html) docs for more.
+## Installing HLS
 
-<!--
-TBD: Add Haskell Docs
-TBD: Haskell formatting docs: haskell.formattingProvider (floskell, ormolu, fourmolu, stylish-haskell)
--->
+Recommended method to [install haskell-language-server](https://haskell-language-server.readthedocs.io/en/latest/installation.html) (HLS) is via [ghcup](https://www.haskell.org/ghcup/install/) (`curl --proto '=https' --tlsv1.2 -sSf https://get-ghcup.haskell.org | sh
+`):
+
+```sh
+ghcup install hls
+which haskell-language-server-wrapper
+```
+
+## Configuring HLS
+
+If you need to configure haskell-language-server (hls) you can add configuration options to your Zed settings.json:
+
+```json
+{
+  "lsp": {
+    "hls": {
+      "initialization_options": {
+        "haskell": {
+          "formattingProvider": "fourmolu"
+        }
+      }
+    }
+  }
+}
+```
+
+See: official [configuring haskell-language-server](https://haskell-language-server.readthedocs.io/en/latest/configuration.html) docs for more.