GG.deals Button wót Archer

Adds a button to the Steam Store and Steamdb pages to quickly find games on GG.deals. There is also a new Steamdb button on GG.deals.
In the future, the best GG.deals price will also be displayed in the game stores. Currently supported are Steam, GOG, and SteamDB. Everything is customizable: whether the page should open in a new tab or in the same tab, and on which pages a button should be added. A Chrome version will also be available at some point when the add-on is "complete".
Please note that this add-on is still very new and actively in development. If you find any bugs, please check if you have the latest version and then report them here on GitHub. This helps me a lot. You can also send me your suggestions for improvement there.
Many thanks to everyone who uses this add-on and helps to improve it!