[Xamarin.Forms] Implementing IsPlaying

[jimbobbennett]

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

Fixes #205

⤵️ What is the current behavior?

The IsPlaying property in the Xamarin.Forms AnimationView wasn't doing anything

🆕 What is the new behavior (if this is a feature change)?

The IsPlaying property is correctly wired up in the renderer. This also marks AutoPlay as obsolete as it replicates the behaviour of IsPlaying="true"

💥 Does this PR introduce a breaking change?

🐛 Recommendations for testing

The Example.Forms sample project has been updated.

📝 Links to relevant issues/docs

#205

🤔 Checklist before submitting

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

[jimbobbennett]

This is a work in progress, the code should work but I can't get the example project to build to test it.

[martijn00]

@jimbobbennett I've merged some stuff and done changes to get the Forms samples compiling again. Can you rebase your PR and check it?

[afk013]

Hi @jimbobbennett could you, when you get a moment rebase the PR please. I have been using your changes for a while now in a locally generated nuget however it would be nice to resume using the public one again especially when bringing Lottie into new projects. Thanks.