tree-sitter-grammars: add proto

The tree-sitter-proto.json file was created by running the update
script as described in tree-sitter/default.nix.

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

···
   tree-sitter-php = lib.importJSON ./tree-sitter-php.json;
   tree-sitter-pioasm = lib.importJSON ./tree-sitter-pioasm.json;
   tree-sitter-prisma = lib.importJSON ./tree-sitter-prisma.json;
+  tree-sitter-proto = lib.importJSON ./tree-sitter-proto.json;
   tree-sitter-pug = lib.importJSON ./tree-sitter-pug.json;
   tree-sitter-python = lib.importJSON ./tree-sitter-python.json;
   tree-sitter-ql = lib.importJSON ./tree-sitter-ql.json;

pkgs/development/tools/parsing/tree-sitter/grammars/tree-sitter-proto.json

···
+{
+  "url": "https://github.com/mitchellh/tree-sitter-proto",
+  "rev": "42d82fa18f8afe59b5fc0b16c207ee4f84cb185f",
+  "date": "2021-06-12T09:29:04-07:00",
+  "path": "/nix/store/dsfx2jxc6nll0324pl3w6qcdv5acvyj5-tree-sitter-proto",
+  "sha256": "001y2z2683fagryqj5f0gs3rcgx2nbw3x3r9afydhss80ihb8zvi",
+  "hash": "sha256-cX+0YARIa9i8UymPPviyoj+Wh37AFYl9fsoNZMQXPgA=",
+  "fetchLFS": false,
+  "fetchSubmodules": false,
+  "deepClone": false,
+  "leaveDotGit": false
+}

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

···
       orga = "MDeiml";
       repo = "tree-sitter-markdown";
     };
+    "tree-sitter-proto" = {
+      orga = "mitchellh";
+      repo = "tree-sitter-proto";
+    };
     "tree-sitter-rego" = {
       orga = "FallenAngel97";
       repo = "tree-sitter-rego";