nvim/lua/plugins/treesitter.lua

-- since `vim.tbl_deep_extend`, can only merge tables and not lists, the code above
-- would overwrite `ensure_installed` with the new value.
-- If you'd rather extend the default config, use the code below instead:
return {
  {
    "nvim-treesitter/nvim-treesitter",
    opts = function(_, opts)
      -- add tsx and treesitter
      vim.list_extend(opts.ensure_installed, {
        "rust",
      })
    end,
  },
  { "nvim-treesitter/playground", dependencies = { "nvim-treesitter/nvim-treesitter" } },
}