feat: refactor and separate LSP/language configurations

lib/languages.nix

@@ -0,0 +1,25 @@
+# From home-manager: https://github.com/nix-community/home-manager/blob/master/modules/lib/booleans.nix
+{lib}: {
+  # Converts a boolean to a yes/no string. This is used in lots of
+  # configuration formats.
+  diagnosticsToLua = {
+    lang,
+    config,
+    diagnostics,
+  }:
+    lib.listToAttrs
+    (map (v: let
+        type =
+          if builtins.isString v
+          then v
+          else builtins.getAttr v.type;
+        package =
+          if builtins.isString v
+          then diagnostics.${type}.package
+          else v.package;
+      in {
+        name = "${lang}-diagnostics-${type}";
+        value = diagnostics.${type}.nullConfig package;
+      })
+      config);
+}