Generated zip won't have plugin-slug folder inside

[shivapoudel]

Describe the bug
Seems like generated zip file while downloading won't have plugin-slug folder.

Steps to Reproduce

1. Implement github action with generate-zip enabled.
2. After all the process is complete, Open zip file!
3. See error, directly all files from trunk is located!

Expected behavior
ZIP file should have plugin-slug.

Additional context

[helen]

#72