[REQUEST] Use environment variable instead of hard-coded URL used by Bytebin and Bytesocks

[MirandaMeow]

The hard-coded Bytebin & Bytesocks related urls are not easily accessble in China mainland, causing very high and unstable latency using the plugin.

For example, on my server, it would take 2~3 minute executing command /spark profler open because of the bad connection.

Would you consider changing the urls to environment variables, so we could customize it link to my docker server so i can avoid the bad connection?

spark-viewer/src/viewer/common/logic/fetch.ts

Line 22 in 9270063

let bytebinUrl = 'https://spark-usercontent.lucko.me/';

spark-viewer/src/viewer/sampler/ws/SocketClient.ts

Line 25 in 9270063

static HOST = 'spark-usersockets.lucko.me';