feat: Add .NET 6 Mobile support

[jeromelaban]

:sparkles: What kind of change does this PR introduce? (Bug fix, feature, docs update...)

Adds .NET 6.0.300 Mobile support, iOS, macOS and watchOS.

There are no archives for catalyst (the objective-C support at the time may not have had it), so net6.0-maccatalyst is not present.

Fixes https://github.com/Baseflow/LottieXamarin/issues/363

:boom: Does this PR introduce a breaking change?

None

:bug: Recommendations for testing

Create a MAUI (Preview 14 or later) or Uno Platform (4.1.9 or later) project and include the Lottie control.

:memo: Links to relevant issues/docs

:thinking: Checklist before submitting

• [x] All projects build
• [ ] Follows style guide lines
• [ ] Relevant documentation was updated
• [ ] Rebased onto current develop

[danielftz]

Could you please tell me what is the status of this?

[jeromelaban]

There's no status for now. The stability and breaking changes introduced by recent .NET 6 Mobile for make it difficult to produce packages. I may revisit this later once things settle down.

[joshardt]

@jeromelaban Do you have any updates? .NET MAUI GA release is available by now.

[jeromelaban]

@joshardt we're not pursuing the update for this repository, and we chose the route of implementing the Skottie wrapper (SkiaSharp.Skottie) instead.