Added uninstall guide for linux in Wiki

[sheikhmishar]

I noticed that the uninstallation procedure in the Wiki was incomplete. I've added additional auxiliary folders that should be deleted during the uninstallation process. Please consider merging these changes into the upstream as github doesn't support pull request for Wiki. Here'e the link:
https://github.com/sheikhmishar/HeroicGamesLauncher/wiki/Removing-Uninstalling-Heroic-Games-Launcher