This change hoists opacity out of props and changes it to a number
instead of an enum.
The change to a number is to make tldraw more flexible for library
consumers who might want more expressivity with opacity than our 5
possible values allow. the tldraw editor will now happily respect any
opacity between 0 and 1. The limit to our supported values is enforced
only in the UI. I think this is limited enough that it's a reasonable
tradeoff between in-app simplicity and giving external developers the
flexibility they need.
There's a new `opacityForNextShape` property on the instance. This works
exactly the same way as propsForNextShape does, except... it's just for
opacity. With this, there should be no user-facing changes to how
opacity works in tldraw. There are also new `opacity`/`setOpacity` APIs
in the editor that work with it/selections similar to how props do.
@ds300 do you mind reviewing the migrations here?
### Change Type
- [x] `major` — Breaking Change
### Test Plan
- [x] Unit Tests
- [ ] Webdriver tests
### Release Notes
[internal only for now]
f2d8fae6ea