Write a coobook

[veeenu]

There are some common recipes that might not apply to all games and probably shouldn't be made first class citizens in hudhook, but which are interesting to keep track of and save a solution for nonetheless. We should write a cookbook with these recipes in hudbook.

I created the cookbook label to track this on issues going forward. Currently, two issues that could go in there are:

• Add a way to check backend at runtime #63
  The proposed solution is pretty simple but can vary from use case to use case and it would be hard to find a solution that's fully universal.
• DX9 ImGui unresponsive #137
  We have figured out that the target game of this use case is just doing whatever the hell it wants with windows messages, and effectively no mouse position that's different from (100, 100) is ever reported anywhere through the normal channels. For this reason, this case needs a solution that hooks other APIs to figure out mouse position. Currently the ImguiRenderLoop facilities allow for that to happen in-band, due to the new on_window_proc and before_render trait methods.