Rename godot-headers to gdextension, move header to top folder

Changes the `<godot/gdextension_interface.h>` include to simply
`<gdextension_interface.h>`.

Refactor and better document the SCons and CMake logic around setting
the paths to the header and API JSON file.

1 files changed, 20 insertions, 0 deletions

diff --git a/gdextension/README.md b/gdextension/README.md
new file mode 100644
index 0000000..1e11f9a
--- /dev/null
+++ b/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
+```