Add base foundation for HTTP, basic GET/POST API, debug command

[Vauff]

Using ISteamHTTP, so no third party dependencies introduced (yet, we probably want a proper JSON implementation later).

D2Lobby2 was used as a starting point after seeing it shared in AM discord, so I've maintained the license headers (we're also GPL anyways).

The c_http command is available in debug builds for testing, some examples:

c_http post "https://httpbin.org/post" "{test: true}"
c_http get "https://httpbin.org/get"
c_http get "https://vauff.com/mapimgs/list.php"