[FEATURE] Support .tgz in adittion to .zip to share hosting with UPM packages

[esperecyan]

Is your feature request related to a problem? Please describe.
In the repository definition JSON file, if anything other than a .zip file is specified for the url in the VPM manifest, the extraction fails.

Describe the solution you'd like
Could you allow specifying a .tgz file for the url in the VPM manifest within the repository definition JSON file.

Describe alternatives you've considered
Since the archive format for UPM is .tgz, I am currently hosting archives separately for UPM and VPM.

Additional context
The archive structure of the .tgz file for UPM matches that of the .zip file for VPM, and it is not a custom format like .unitypackage.