Source: https://stefma.medium.com/how-to-store-a-android-keystore-safely-on-github-actions-f0cef9413784
Download GPG: https://gpgtools.org/
# encrypt file with a password (saved as release.keystore.asc)
# save string in github secrets etc.
gpg -c --armor release.keystore
# usage on github actions
echo "${{ secrets.RELEASE_KEYSTORE }}" > release.keystore.asc
gpg -d --passphrase "${{ secrets.RELEASE_KEYSTORE_PASSPHRASE }}" --batch release.keystore.asc > android/app/release.keystore