feat(editor): time based image overlays

[ekuleshov]

PR Checklist (Required)

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• The commit message follows our guidelines: https://github.com/hm21/pro_image_editor/blob/stable/CONTRIBUTING.md#style-guides
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• I have updated the CHANGELOG.md file with my changes (For the version, you can use X.X.X, I will later bump it after it's merged).
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PR Type

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• Bugfix
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Current Behavior

Issue Number: N/A

New Behavior

Breaking Changes?

Does this PR introduce a breaking change?

• Yes
• No

Additional Information

Based on the discussion at #53 (reply in thread)

I replaced image overlay in the example app with time based overlay.
The example app works on Android. I am unable to run iOS and macos builds due to recent changes in the pro_image_editor see a bit more info in #88