reordered the libs

lib/godot-cpp/gdextension/README.md

@@ -0,0 +1,20 @@
+# GDExtension header and API
+
+This repository contains the C header and API JSON for
+[**Godot Engine**](https://github.com/godotengine/godot)'s *GDExtensions* API.
+
+## Updating header and API
+
+If the current branch is not up-to-date for your needs, or if you want to sync
+the header and API JSON with your own modified version of Godot, here is the
+update procedure used to sync this repository with upstream releases:
+
+- Compile [Godot Engine](https://github.com/godotengine/godot) at the specific
+  version/commit which you are using.
+  * Or if you use an official release, download that version of the Godot editor.
+- Use the compiled or downloaded executable to generate the `extension_api.json`
+  and `gdextension_interface.h` files with:
+
+```
+godot --dump-extension-api --dump-gdextension-interface
+```