feat(install)!: generate from json instead of requiring node

Problem: Many parsers require node/npm to evaluate the `grammar.js`
before being able to generate a parser from it.

Solution: Generate from `grammar.json` instead, which is fully resolved.
Drops `node` and `npm` as (optional) requirements for nvim-treesitter.

Note that this requires parsers to commit the generated json iff the
grammar requires evaluation (which is currently the case for all tracked
languages).

plugin/nvim-treesitter.lua

@@ -38,7 +38,7 @@ end, {
 
 api.nvim_create_user_command('TSInstallFromGrammar', function(args)
   require('nvim-treesitter.install').install(args.fargs, {
-    generate_from_grammar = true,
+    generate = true,
     force = args.bang,
   })
 end, {