provides setting the mixedContentMode on Android

[flyaswind]

i found no settings for the mixedContentMode，when a https website contains http , the webview appears empty
i tried to provide settings for the mixedContentMode , and set the mixedContentMode on WebSettings on the Android platform

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[stuartmorgan-g]

Thanks for the contribution! It looks like this is essentially the same as #3867; see discussion there. I would suggest closing this and following up there, unless you believe there's some specific way this improves over that version that couldn't be incorporated.

[ditman]

Unfortunately we’re unable to accept PRs without a signed CLA. If you sign the CLA in the future, please comment to let us know, and we can re-open this PR.

Alternatively, you can take a look at these related PRs, maybe they can use your help to get landed:

• [webview_flutter] add mixedContentMode option for Android WebView #2468
• [webview_flutter] add COMMON support for Android WebView initializing #3721