docs: add release checklist

Author: wlk-r

RELEASE.md

@@ -0,0 +1,8 @@
+# Release Checklist
+
+- Build zip: `blender.exe --command extension build --source-dir . --output-dir ./dist`
+- In Blender, remove any dev symlink/junction install of `blender_bridge`
+- Install `dist/blender_bridge-<version>.zip` via `Install from Disk`
+- Confirm no manifest warning appears
+- Enable addon and verify toggle, `Copy Agent Instructions`, and HTTP POST to `http://localhost:9876`
+- Re-enable dev symlink/junction after release testing if needed