Adds share URL, download PGN and GIF Options to the broadcast game screen

Preview:

Remarks:

• I refactored the GIF functionality from study into game_share_service and reused it for broadcasts.
• The broadcast name and round name are not necessary for the URL, but I believe including them is better, as it helps to humanly read the URL.
• I decided against adding the screenshot position option. I can implement it if you think its needed, but I think this feature is unnecessary on mobile devices.