neovim: expose derivations instead of just src

which is strictly better as you can still access the original url via
`neovim-unwrapped.treesitter-parsers.c.src`

Initial motivation started while developing on neovim via the following
devShell:
https://github.com/nix-community/neovim-nightly-overlay/blob/0fcef258e524f08cdcaaa163c37f14b892f6fd88/flake/dev/devshells.nix#L32

I've had neovim built from source complaining about missing grammars.
I am not sure why, I think it's because we disable bundled dependencies.
Exposing the derivations avoid users having to express the grammars
themselves.

This changes the type for outside consumers but for the better I think.
I dont know anyone using it ?

pkgs/by-name/ne/neovim-unwrapped/package.nix

@@ -123,18 +123,31 @@ stdenv.mkDerivation (
 
     inherit lua;
     treesitter-parsers =
-      treesitter-parsers
-      // {
-        markdown = treesitter-parsers.markdown // {
-          location = "tree-sitter-markdown";
-        };
-      }
-      // {
-        markdown_inline = treesitter-parsers.markdown // {
-          language = "markdown_inline";
-          location = "tree-sitter-markdown-inline";
-        };
-      };
+      lib.mapAttrs
+        (
+          language: grammar:
+          tree-sitter.buildGrammar {
+            inherit (grammar) src;
+            version = "neovim-${finalAttrs.version}";
+            language = grammar.language or language;
+            location = grammar.location or null;
+          }
+        )
+        (
+          treesitter-parsers
+
+          // {
+            markdown = treesitter-parsers.markdown // {
+              location = "tree-sitter-markdown";
+            };
+          }
+          // {
+            markdown_inline = treesitter-parsers.markdown // {
+              language = "markdown_inline";
+              location = "tree-sitter-markdown-inline";
+            };
+          }
+        );
 
     buildInputs = [
       libuv
@@ -226,14 +239,7 @@ stdenv.mkDerivation (
     + lib.concatStrings (
       lib.mapAttrsToList (language: grammar: ''
         ln -s \
-          ${
-            tree-sitter.buildGrammar {
-              inherit (grammar) src;
-              version = "neovim-${finalAttrs.version}";
-              language = grammar.language or language;
-              location = grammar.location or null;
-            }
-          }/parser \
+          ${grammar}/parser \
           $out/lib/nvim/parser/${language}.so
       '') finalAttrs.treesitter-parsers
     );