feat: allow editing on iOS

[tgpetrov]

@msaravitz created a PR:

PR Checklist

• [x] The PR title follows our guidelines: https://github.com/NativeScript/NativeScript/blob/master/CONTRIBUTING.md#commit-messages.
• [x] There is an issue for the bug/feature this PR is for. To avoid wasting your time, it's best to open a suggestion issue first and wait for approval before working on it.
• [x] All existing tests are passing
• [x] Tests for the changes are included

What is the current behavior?

https://github.com/NativeScript/nativescript-camera/issues/180

What is the new behavior?

Setting the allowsEditing option to true adds a square crop to images on iOS on the "Retake" "Use Photo" screen. This also allows users to "zoom/crop" after the picture has been taken but before it is used. Implements #[180].

[etabakov]

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Regards from the whole team 🥇