## Summary of the Pull Request
This adds a new appxmanifest for 'Windows Terminal (Preview)' and links the resources.
Code-wise, split up `WindowsTerminalReleaseBuild` into...
- WindowsTerminalOfficialBuild: [true, false]
- WindowsTerminalBranding: [Dev, Preview, Release]
Added a comment about that in release.yml
## Validation Steps Performed
used msbuild to build...
- [X] Dev
- [X] Preview
- [X] Release
then checked the msix for the correct name/icon.