feat(cropper-selection): aspectRatio reactivity

[NamesMT]

Reopen of #1161

Resolves #1124

Summary

What kind of change does this PR introduce? (check at least one)

• Bugfix
• Feature
• Code style update
• Refactor
• Docs
• Build-related changes
• Other, please describe:

If changing the UI of the default theme, please provide the before/after screenshot:

Does this PR introduce a breaking change? (check one)
Maybe?, theorically if user allowed input to change the aspect-ratio multiple times before commiting an action, then previously the width/height is only recalculated once, but because it is now reactive, the width/height would recalculated and grow multiple times.
#1164 would improve the UX on this part where the selection area would not grow too much.

• Yes
• No

If yes, please describe the impact and migration path for existing applications:

The PR fulfills these requirements:

• When resolving a specific issue, it's referenced in the PR's title (e.g. fix #xxx[,#xxx], where "xxx" is the issue number)
  It is referenced in commit body

You have tested in the following browsers: (Providing a detailed version will be better.)
Tested with playground

• Chrome
• Firefox
• Safari
• Edge
• IE

If adding a new feature, the PR's description includes:

• A convincing reason for adding this feature
• Related documents have been updated
• Related tests have been updated

To avoid wasting your time, it's best to open a feature request issue first and wait for approval before working on it.

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