Introduce CI and templates

[arves100]

• Introduce ISSUE_TEMPLATE and PR_TEMPLATE to further help bug reports and PR handling (this can be done in github docs)
• Introduce a basic CI workflow that checks for the following:

1. Make sure that the server compiles fine in development configuration for Linux, Windows and MacOSX
2. Make sure that the Windows deployment works correctly
3. Create a sample workflow for deployments of releases (libofflinemod.so) to be bundled with the Offline mod patches (NOTE: Decide which release versioning to do and how)
4. If the pointer in "packet-generator" has been modified, make sure to run "generate.py" (or more equivalent scripts) and make sure that the generation does pass otherwise throw an error