treesitter: move autogroup definition to augroup module

Signed-off-by: NotAShelf <raf@notashelf.dev>
Change-Id: I1a2f5e47b4d9457a91a84802944ea06f6a6a6964

Author: NotAShelf

modules/plugins/treesitter/config.nix

@@ -21,9 +21,18 @@ in {
 
       treesitter.grammars = optionals cfg.addDefaultGrammars cfg.defaultGrammars;
 
-      pluginRC.treesitter-autocommands = entryAfter ["basic"] ''
-        vim.api.nvim_create_augroup("nvf_treesitter", { clear = true })
+      # Define the autogroup for treesitter here rather than in the Lua snippet
+      # to allow overriding more easily. Should be highly unlikely that a user
+      # wants to override, but not impossible.
+      augroups = [
+        {
+          enable = true;
+          name = "nvf_treesitter";
+          clear = true;
+        }
+      ];
 
+      pluginRC.treesitter-autocommands = entryAfter ["basic"] ''
         ${lib.optionalString cfg.highlight.enable ''
           -- Enable treesitter highlighting for all filetypes
           vim.api.nvim_create_autocmd("FileType", {
@@ -54,6 +63,7 @@ in {
             callback = function()
               vim.wo[0][0].foldmethod = "expr"
               vim.wo[0][0].foldexpr = "v:lua.vim.treesitter.foldexpr()"
+
               -- This is optional, but is set rather as a sane default.
               -- If unset, opened files will be folded by automatically as
               -- the files are opened