docs(hls): init HLS doc; document how to disable HLS (#317)

* docs(hls): init HLS doc; document how to disable HLS

A start to #245

* edit

---------

Co-authored-by: Sridhar Ratnakumar <srid@srid.ca>

doc/hls.md

@@ -0,0 +1,46 @@
+---
+order: -8
+---
+
+# IDE configuration (HLS)
+
+By default, #[[devshell]] of haskell-flake projects includes [haskell-language-server](https://github.com/haskell/haskell-language-server) and [a few other tools by default](https://github.com/srid/haskell-flake/blob/988a78590c158c5fa0b4893de793c9c783b9d7e9/nix/modules/project/defaults.nix#L23-L29).
+{#disable}
+## Disabling `haskell-language-server`
+
+> [!tip] Default options
+> Alternatively, disabling the [[defaults|default options]] (i.e., `haskellProjects.<proj-name>.defaults.enable = false;`) automatically removes HLS.
+
+HLS is included as part of the default value of `devShell.tools` options. You can override this default by overriding it, for e.g.:
+
+```nix
+{
+  haskellProjects.<proj-name> = {
+    # NOTE: This is 'defaults.devShell.tools', not 'devShell.tools'
+    defaults.devShell.tools = hp: with hp; {
+      inherit
+        cabal-install
+        ghcid;
+    };
+  };
+}
+```
+
+Alternatively, you can set it to `null` at a project-level:
+
+```nix
+{
+  haskellProjects.<proj-name> = {
+    # NOTE: This is 'devShell.tools', not 'defaults.devShell.tools'
+    devShell.tools = {
+      haskell-language-server = null;
+    };
+  };
+}
+```
+
+{#disable-plugins}
+## Disabling HLS plugins
+
+>[!warning] TODO
+> See here for current status: <https://github.com/srid/haskell-flake/issues/245>