Add overflow menu to image viewer to open image in image gallery

[TheLastProject]

Apparently some people really need to use their regular gallery to fake it being the official app for some stores with abusive management that insists on "official app only" so they can track people more.

If we add an overflow menu (3 dots in the top right) to open the image in the gallery we can support both the in-app viewer and this use case fairly easily.

Until implemented, users who really need the gallery app should export data, uninstall, install v2.42.1 and import their data.

@TheLastProject
Please leave the option to select an external image viewer. There are a couple of stores that require you to present a barcode from their app. I solved the problem by saving the screenshots in Catima. And now I can't open these screenshots to the full screen so that it looks like it's the app of this store.

Originally posted by @dymn in #2156

[devmaiter]

Hi, I'd like to work on this if it's still open

[TheLastProject]

Sure, go for it :)

[KamiDaga]

Hello, is this issue still open? I would like to try work on this.

[dymn]

I thought that if I opened the image to the full screen inside the application, that would be enough.