Provide a convenient way to access a writable directory for extensions.
This will typically be accessed via:
bpy.utils.extension_path_user(__package__, create=True)
This API is provided as some extensions on extensions.blender.org
are writing into the extensions own directory which is error prone:
- The extensions own directory is removed when upgrading.
- Users may not have write access to the extensions directory,
especially with "System" repositories which may be on shared network
drives for example.
These directories are only removed when:
- Uninstalling the extension.
- Removing the repository and its files.