…ble builds [ci skip]

Also enable support for x86_64 ABI and bump `versionCode` for Android builds. 'local.properties' has been removed, as it must not be tracked by git and can be unintentionally commited with other changes.

* fix: satisfy the flathub linter 😭

* Fix the 0.99.0-beta4 release date 

This version was released on May 3, 2022, 1:46 AM UTC

* chore: add instructions on how to get the game data working

* Remove CS+ screenshots, add valid content rating and screenshots caption

The engine is not distributed with the CS+ game data, so this screenshots are not correct for the most of the flatpak users. The content rating is just copy-pasted from the NXEngine package and and should probably be changed in the future

Also debug builds have `(debug)` in the app name, documents provider label and authority. This is done to make it possible to install custom debug builds without uninstalling the official one.

glFinish waits until rendering is complete, there usually isn't a good reason to do this.
Removing it improves performance on (very) low end hardware.