Add gateway urls

[slatinsky]

Fixes:

[22:18:45.199] ☎️  Wumpus In The Middle: Unrecognized websocket url: https://gateway-us-east1-d.discord.gg/?encoding=etf&v=9&compress=zlib-stream
127.0.0.1:50178 <- WebSocket binary message <- gateway-us-east1-d.discord.gg:443/?encoding=etf&v=9&compress=zlib-stream

gateway-us-east1-a.discord.gg, gateway-us-east1-b.discord.gg and gateway-us-east1-c.discord.gg urls were guessed based on: https://github.com/Cyanic76/Hosts/blob/f139ae4133909b406cbdf2abc48eacceabbae91f/corporations/Social/discord.txt#L16C1-L19C38

Note: regex may be a better solution

[Roachbones]

Nice, I wasn't sure where to find more gateway URLs. I think you have to remove the :443s, though, since the port number isn't included in flow.request.url.

[slatinsky]

port 443 removed in the latest commit