Add listner for attachment download

Hi there!

I wanted to reach out to see if it would be possible to implement a listener for downloads specifically for headers that have the Content-Disposition set to attachment (for openInWebView).

It would be great to intercept those requests and manage them using @capacitor/filesystem and @capacitor/file-transfer (or download them via inappbrowser). If the header is set to "inline," the inappbrowser attempts to display the file, but what I really need is to download it (excel, word documents, etc).

Something similar to what Cordova offers with its [InAppBrowser - addEventListener](https://cordova.apache.org/docs/en/latest/reference/cordova-plugin-inappbrowser/index.html#inappbrowseraddeventlistener).

I've tried using the browserPageNavigationCompleted event, but unfortunately, it doesn't trigger in these cases.

Thank you so much for considering this!