feat (APKMirror downloader): Provide Help dialog to users

[KobeW50]

Feature description

A help button at the top of the embedded browser that displays helpful information for users that don't know what to do. Here is a prototype:

Motivation

APKMirror is a confusing and disorienting website for inexperienced users. New users may not even understand why they are being brought to APKMirror, or what the site does.

Acknowledgements

• I have checked all open and closed feature requests and this is not a duplicate
• I have chosen an appropriate title.
• All requested information has been provided properly.

[oSumAtrIX]

I am not sure how feasible this is from an architectural pov. The downloader webView() api is generic and does not have a feature to inject components like this. Neither don't I think it makes to overspecialize the api for such a purpose. Instead, a downloader can come with a description, similar to patches do. This way a downloader can describe what it does, how it works, what it needs from the user and so on.