Make an example that works with the https://github.com/gioui/ examples

[gedw99]

RunWithExternalLoop looks great and should work with gio.

https://github.com/gioui/gio-example

If i get time i will make one, but just making this issue for collaboration.

[andydotxyz]

I started to add a "toolkit specific" section under "API" of the README (before "Run in another toolkit") - feel free to add Gio or other examples in there. I don't know it well enough to suggest how it would be done.

[gedw99]

Thanks @andydotxyz