feat: add parser tiers

Tier 1: Stable
Tier 2: Core (maintained by org members)
Tier 3: Community (maintained by external contributors, to varying
degree)
Tier 4: Unsupported (lacking active maintainer or declared
experimental); skipped in lockfile update and ignored for automatic
install by default

lua/nvim-treesitter/config.lua

@@ -10,7 +10,7 @@ local M = {}
 local config = {
   auto_install = false,
   ensure_install = {},
-  ignore_install = {},
+  ignore_install = { 'unsupported' },
   install_dir = vim.fs.joinpath(vim.fn.stdpath('data'), 'site'),
 }