Add ability to customize ModalBottomSheet appearance in BottomSheetOverlay

[chriswiesner]

I've read that you're not accepting external contributions - raised the limitations of the BottomSheetOverlay in a discussion - but thought it might be a quick win if we could incorporate those changes directly.

This change adds the ability to customize the ModalBottomSheets appearance:

• dragHandle
• sheetShape
• containerColor

Additionally it adds the ability to specify if the partiallyExpanded state of the sheet should be skipped. (There are use cases where the sheet should directly expand to it's full height)

Would be great if this could be incorporated.
Let me know if the optional parameters in the existing constructors are fine or there should be dedicated ones.

[salesforce-cla]

Thanks for the contribution! Before we can merge this, we need @chriswiesner to sign the Salesforce Inc. Contributor License Agreement.

[chriswiesner]

I figured that these customizations could also be done by creating a custom BottomSheetOverlay as all dependencies of it are public.
So, probably it is not necessary to incorporate these in the library 🤔

[ZacSweers]

I'm open to adding these, though I wonder if there's a way to make this more generic (maybe a @Composable () -> BottomSheetState param?). CC @stagg for thoughts

[stagg]

I'm open to adding these, though I wonder if there's a way to make this more generic (maybe a @Composable () -> BottomSheetState param?). CC @stagg for thoughts

We could add a "DialogOverlay" where one could supply their own content and trigger the dismiss when appropriate. Mostly as a simple Overlay impl with prebuilt back handling and dismiss logic.

I'm cool with this for the bottom sheet though, not much more we can do to make it agnostic while still being a ModalBottomSheet.

[stagg]

Lets remove the full qualification of Shape here and on the public constructors.

[ZacSweers]

Thanks!