What is it?

• Bugfix
• Feature
• Codebase improvement

Description of the changes in your PR

• Configured Fastlane (uses https://github.com/naveensingh/fastlane-plugin-fossify for easy maintainance)
• Reformatted CHANGELOG.md as per https://github.com/olivierlacan/keep-a-changelog
• Renamed prepaid flavor to gplay
• Added release workflows for foss and gplay flavor

This is the first step towards fully automated releases.