Provide the Hash of the Signing Certificate for People Downloading from Github

[KaiserCalm]

Is your feature request related to a problem? Please describe.
I've been using Obtanium together with AppVerifier to download most of my apps. A lot of apps don't have the hash listed which is making it difficult to verify the origin of their apks.

Describe the solution you'd like
Provide the hash in the git repo's README.md so people downloading the APK from Github can make sure it is comming from the developer.

Describe alternatives you've considered
Using the Google Play version of the app or not verifying the hash. Neither option really meets my needs.

Additional context
An example from Thunderbird for Android:
https://github.com/thunderbird/thunderbird-android#security