refactor: re-layput project

- move assets (raw jsons, icons, meshes and i18n data) into the root of repo.
- move script into the root of repo.
- modify blender manifest according to this changes.
- optimize gitignore.

scripts/README.md

@@ -0,0 +1,27 @@
+# Tools
+
+These tool scripts is served for BBP_NG specifically. We use Astral UV with a single Python project file to manage these tools. You can browse their usage in this file.
+
+## Build Icons
+
+Build essential icons used by BBP_NG in Blender.
+
+Execute `uv run build_icons.py`
+
+## Build JSONs
+
+Compress BME prototype JSON files into smaller size.
+
+Execute `uv run build_json.py`
+
+## Validate BME Prototype
+
+Validate the correction of BME prorotype JSON files.
+
+Execute `uv run validate_json.py`
+
+## Extract BME Translation
+
+Extract the translation template from BME prorotype JSON files.
+
+Execute `uv run extract_json.py`