tree-sitter-grammars: add grammarsScope package set

This allows overriding grammars with overlays

pkgs/development/tools/parsing/tree-sitter/default.nix

@@ -1,6 +1,7 @@
 {
   lib,
   stdenv,
+  newScope,
   fetchFromGitHub,
   fetchFromGitLab,
   fetchFromSourcehut,
@@ -68,6 +69,14 @@ let
   */
   builtGrammars = lib.mapAttrs (_: lib.makeOverridable buildGrammar) grammars;
 
+  /**
+    # Extensible package set for tree-sitter grammars.
+    # Provides .override and .extend for customization.
+    # Note: Use builtGrammars (not this) when iterating over grammars,
+    # as this includes package set functions alongside derivations
+  */
+  grammarsScope = lib.makeScope newScope (self: builtGrammars);
+
   # Usage:
   # pkgs.tree-sitter.withPlugins (p: [ p.tree-sitter-c p.tree-sitter-java ... ])
   #
@@ -183,6 +192,7 @@ rustPlatform.buildRustPackage (finalAttrs: {
       grammars
       buildGrammar
       builtGrammars
+      grammarsScope
       withPlugins
       allGrammars
       ;