allow setting minimum window size

[cmyr]

This will be very similar in implementation to #587.

[luleyleo]

I've implemented it but I'm (again) not sure about naming 😅

The function to set a windows initial size is called WindowDesc::window_size thus is would be consistent to call the function for minimal size window_min_size but it seems odd to me when another function is called WindowDesc::title and not window_title.

Also based on the discussion in #697 it would make most sense to call it with_min_size and with_title.

Thus I would call the function WindowDesc::with_min_size in my PR and then make another one to rename all other methods of WindowDesc to builder style naming

[cmyr]

yea, naming is a disaster.

something like WindowDesc is only a builder, so I don't feel too bad about not using with everywhere. That's mostly a problem with widgets. I would be happy with either min_size or with_min_size.

[cmyr]

This is now added in druid, but we still need druid-shell support for mac & windows.

[xStrom]

This was implemented for Windows by #727. There's also a macOS specific issue for this at #714.

[cmyr]

okay, lets close in favour of #714