Adding Bangle.getAppRect? Widget bar size...

@andrewg_oz thanks - i'll change those g.theme docs.

I guess one thing I'm imagining (and I may implement this at some point) is that a 'large widgets' app could replace Bangle.loadWidgets and then wrap every widget's draw call in a function that drew it to an offscreen buffer and then doubled the size. It wouldn't be a hard thing to do and I think for some users it might be valuable.

But yes, asking widget developers to handle different sizes would increase a lot of bloat and extra effort needed. I'm not sure it's a sensible thing to do either.