Fix wasm compilation/rendering

[Fabi019]

Thank you for this great UI library! While trying it out in a WASM environment I found and fixed some small issues:

• Compilation errors due to some non wasm compatible types used (muda::Menu, std::time::Instant)
• No render output due to self.paint_state not getting set to Initialized without paint called
• Invisible text on label/buttons in the webgpu example -> Manually set the font_family to "Fira Sans"

[umbrageodotus]

LGTM

[jrmoulton]

Can you speak to the accuracy of doing this. Is this always true?

[Fabi019]

During testing I noticed that when setting render_ready to always true the paint_state was in pending for some cycles and then got to initialized. Without, the paint_state was always stuck in pending. While looking at it again now, I suspect the actual reason might be because the last_presented_at only gets set inside the condition. So when renderer_ready is false render_frame gets called without any/very low delay in between thus preventing the initialization. To confirm, I moved the self.last_presented_at = Instant::now(); outside of the condition and with that it also works with the original renderer_ready flag. Maybe that would be the better fix instead?

[umbrageodotus]

I think it would be but

[jrmoulton]

Thanks for doing this! Just one question