feat: Add signature checks

[oSumAtrIX]

Feature description

Utility functions that check for the GPG signature of patches files

Motivation

Same as https://github.com/ReVanced/revanced-manager/issues/2082

Acknowledgements

• [X] I have checked all open and closed feature requests and this is not a duplicate.
• [X] I have chosen an appropriate title.
• [X] All requested information has been provided properly.