decrease build time

[unixfox]

Area for improvements:

• fetch .jar directly instead of mvn get
  • push jar of public repo to github releases: https://github.com/PGMDev/Events/blob/master/.github/workflows/ci.yml
• use cache layers like maps don't change that often and same for multiple default binaries
  • tutorial here: https://dev.to/dtinth/caching-docker-builds-in-github-actions-which-approach-is-the-fastest-a-research-18ei