Add the Giant Stopwatch application

• The app complies with the inclusion criteria
• The original app author has been notified (and does not oppose the inclusion) - yes https://github.com/arpruss/simplestopwatch/issues/1#issuecomment-782707005
• All related fdroiddata and RFP issues have been referenced in this merge request
• The upstream app source code repo contains the app metadata (summary/description/images/changelog/etc) in a Fastlane or Triple-T folder structure
• Builds with fdroid build
• Releases are tagged

Tested the app by installing local build via adb.