* refactor(plugin_packager): update Assets method to use OS-independent path separator
- Modified the Assets method in FSPluginDecoder and PluginDecoderHelper to accept a separator argument, ensuring compatibility across different operating systems.
- Updated the Assets method in ZipPluginDecoder to use '/' as the separator for zip files, addressing issue #166.
- Improved code readability by adjusting formatting in the ZipPluginDecoder struct.
* fix: add tests