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/bme.py

@@ -0,0 +1,3 @@
+import enum
+from typing import Optional, Self
+from pydantic import BaseModel, RootModel, Field, model_validator, ValidationError