Provide version information using GET /version endpoint
Version information is passed using linker to executable by the CI. Information is provided to quickly identify how the running server executable was build and whether or not it is current.
For testing, the CI has been temporarily modified to also build in feature branches. The corresponding build job can be found at https://gitlab.akamu.de/akamu/game-server-go/-/jobs/5666 and the executables for windows, linux and mac can be downloaded.
Closes #12 (closed)