README.md Fix for Go install

[r0bm3]

Hey All -
This isn't an issue, but the README.md needs to be updated for the GO install. I'd have branched and PR but the repo's locked down so please excuse.

README.md
Line 13
Is: 'If you have Go you could also simply go get github.com/itzg/rcon-cli && rcon-cli -h.'
Should be: 'If you have Go you could also simply go install github.com/itzg/rcon-cli@latest && ${HOME}/go/bin/rcon-cli -h.'

[itzg]

Ah yes. That command was from ancient times 😉