Wrap WebViewClient to provide custom web view client implementation

[saperi22]

Summary of changes

• Address issue reported here
• Introduce PopupBridgeWebViewClient that merchants can implement to extend WebViewClient functionality.

Checklist

• Added a changelog entry

Authors

List GitHub usernames for everyone who contributed to this pull request.

• @seviraristocrat @tdchow @saperi22

[seviraristocrat]

Perhaps, it is possible to make this class as a wrapper that receives library user WebViewClient implementation as a delegate?

class PopupBridgeWebViewClient(
    private val delegate: WebViewClient? = null
) : WebViewClient() {

    override fun onPageFinished(view: WebView?, url: String?) {
        super.onPageFinished(view, url)
        setVenmoInstalled(view, view?.context?.isVenmoInstalled() == true)
        delegate?.onPageFinished(view, url)
    }

    // same for other methods
}

I know it is painful to override all the calls with delegate calls inside, but this approach doesn't limit library users to inheriting strictly from PopupBridgeWebViewClient.

[saperi22]

@seviraristocrat Thanks for reporting the bug and suggesting the solution!