feat(client): notify about unsupported node version

Author: MunifTanjim

lua/copilot/client.lua

@@ -46,6 +46,14 @@ function M.get_node_version()
       table.concat(vim.fn.systemlist(config.get("copilot_node_command") .. " --version", nil, false)),
       "v(%S+)"
     )
+
+    local node_version_major = tonumber(string.match(copilot_node_version, "^(%d+)%."))
+    if node_version_major < 16 then
+      vim.notify(
+        string.format("[Copilot] Node.js version 16.x or newer required but found %s", copilot_node_version),
+        vim.log.levels.ERROR
+      )
+    end
   end
   return copilot_node_version
 end