[WIP] Add basic simulator support

[byronwasti]

This isn't a completed feature yet, but I think its a good baseline to get us started.

I'm wondering about the functionality of this feature: how are people going to use it and what form does it need to be in?

Currently it is implemented as a submodule in a workspace, but I'm not convinced that is the best form for it to take.

[jamwaffles]

Awesome! Thanks for doing this. Even works on Windows Subsystem for Linux!

Can you fix the build though? I think just installing libsdl2-dev should be fine if you want to build simulator, but I'm more interested in making sure embedded-graphics continues to build and push docs ok. Just adding -p embedded-graphics to the cargo commands should be enough.

Currently it is implemented as a submodule in a workspace, but I'm not convinced that is the best form for it to take.

I'm on the fence about this one. It might make more sense as a separate repo, but on the flipside it's useful to distribute a simulator with the library to test things without needing a hardware display. I tinker with this lib at work where I don't have a display to work on for example. It may also be useful in the future as part of the CI infra. Let's leave it where it is for now. It can easily be split out later :)

[jamwaffles]

Sorry for letting this sit, didn't realise you'd pushed fixes. This should be a good base to build on even if there's a better place for it to live in the future. Thanks!