Add Electron Forge
Changes:
- Added Electron Forge build pipeline and package generation of .msi, .dmg, .deb, .rpm, and .zip for Windows/Mac/Linux targets
- Code signing for Mac builds
- Created Docker container for build environment
- Setup S3 file hosting
- Setup Gitlab CI and runner configuration
- Removed GPLv3 licenses for certain sub-projects, switching to MIT used by the whole repo
- Updated dependencies and package version