updated readme for v3.0.0

fixed version of nuget badge

added build script for GitHub Actions

updated readme for 1.2.0 release

Merge branch 'main' of https://github.com/Synnotech-AG/Synnotech.Data…

…baseAbstractions into main

updated readme for 1.1.0 release

Merge branch 'main' of https://github.com/Synnotech-AG/Synnotech.Data…

…baseAbstractions

added script for creating nuget packages