[webview_flutter] Added possibility to activate the zoom webview - IOS & Android

[Dn-a]

Description

I have added the ability to enable zooming on IOS and Android WebView.
replaces previous pull request #1459

Related Issues

n/a

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• I read the Contributor Guide and followed the process outlined there for submitting PRs.
• My PR includes unit or integration tests for all changed/updated/fixed behaviors (See Contributor Guide).
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Breaking Change

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[Dn-a]

@googlebot I fixed it.

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[stuartmorgan-g]

Thanks for the submission! We’re currently working through a large backlog of PRs, and this will require non-trivial review, so it will take some time before we’re able to review it. As explained in CONTRIBUTING.md, votes for the corresponding issue are the primary way we’re prioritizing non-trivial reviews, so we encourage you to file an issue and associate it with this PR.

We apologize for the long delay in triaging this PR. We’re in the process of overhauling our PR triage system to respond much more quickly, as well as working through the backlog.

[stuartmorgan-g]

(Cross-referencing for the future: it looks like there's overlap between this, #2451, and #3325)

[stuartmorgan-g]

Closing, as this was updated and tested in #3325. Thanks again for the submission!