## Link to GitHub Issue or related Pull Request, if one exists
Fixes#134
## Description of change
Add ImGui DX11 backend implementation, and integrate into the spice
overlay.
The tricky part is that some of the Unity games:
1. Launch multiple windows, and
2. Can be resized (even full screen games launch at a certain resolution
and then expand to fit desktop resolution)
3. lazy load DX11 DLLs
This PR also adds screenshot functionality, but screen resize is not
implemented.
## Testing
Seems to be working for most games. Need to do final tests for:
- [x] CCJ (attract movie plays as well)
- [x] Busou Shinki (title movie plays)
- [x] MFG
- [x] QuizKnock
- [x] Polaris Chord
- [x] check dx9 for regression
bicarus