Build & ship complete plugin package in CI

[charneykaye]

• main branch CI for this repository has a build & ship pipeline for XJUnrealPlugin similar to https://github.com/xjmusic/xjmusic/actions/workflows/workstation_distro.yml
  • checkout and build the engine project to include the required library and source code in the XJUnrealPlugin distribution
  • build & ship distribution for 4 platforms: Windows, Mac (Silicon), Mac (Intel), and Linux