## Link to GitHub Issue, if one exists
n/a
## Description of change
Change the dark brown colors used in widget backgrounds to dark gray.
Decrease the in-game overlay transparency (more opaque): 80% -> 96%.
## Testing
Tested cfg and in-game overlay.
## Link to GitHub Issue, if one exists
n/a
## Description of change
Functionally, no change.
Move ImGui library files around so that they mirror how they are
structured in imgui releases. This will make it easier to migrate to a
future version of ImGui.
Add a handful of static asserts to check that we have the necessary
features enabled / disabled in imgui header.
## Compiling
👍
## Testing
Tested 32-bit overlay, 64-bit overlay, TDJ, and UFC overlays, and
spicecfg.
Interesting finds during ImGui testing (not part of this PR, but for
future reference when upgrading imgui version):
* Updating dx9 backend to the newest causes TDJ to stop rendering the
overlay completely (fine in UFC or any other game)
* Omitting `IMGUI_USE_BGRA_PACKED_COLOR` causes spicecfg software
renderer to use the wrong color (RGB format parsing error probably)
* At some point - v1.90? the `About` and `Licenses` buttons in spicecfg
stop responding after an upgrade, maybe our improper usage of MenuItem?
* Using the docking branch of ImGui is not required but we should just
stick to it for multi-viewport functionality which we may want to use
later.
bicarus-dev