WIP: Steamcommunity screenshot/artwork extractor

[GiovanH]

For #7565.

Currently handles screenshot and artwork although obviously very barebones.

[gallery-dl][debug] Version 1.30.0-dev - Git HEAD: 1866f8b9
[gallery-dl][debug] Python 3.11.5 - Windows-10-10.0.19045-SP0
[gallery-dl][debug] Configuration Files []
[gallery-dl][debug] Starting DownloadJob for 'https://steamcommunity.com/sharedfiles/filedetails/?id=296316110'
[SteamCommunity][debug] Using SteamCommunitySharedfileExtractor for 'https://steamcommunity.com/sharedfiles/filedetails/?id=296316110'
[urllib3.connectionpool][debug] Starting new HTTPS connection (1): steamcommunity.com:443
[urllib3.connectionpool][debug] https://steamcommunity.com:443 "GET /sharedfiles/filedetails/?id=296316110 HTTP/1.1" 200 10041
[urllib3.connectionpool][debug] Starting new HTTPS connection (1): images.steamusercontent.com:443
[urllib3.connectionpool][debug] https://images.steamusercontent.com:443 "GET /ugc/567770337564660542/8552FC9551546163E36D29B0512097A7084C8B1B/ HTTP/1.1" 200 176939
.\gallery-dl\SteamCommunity\The Stanley Parable\567770337564660542_8552FC9551546163E36D29B0512097A7084C8B1B.jpg