Add a possibility to preview image in filepicker mode

[Managor]

Checklist

• [x] I made sure that there are no existing issues - open or closed - to which I could contribute my information.
• [x] I made sure that there are no existing discussions - open or closed - to which I could contribute my information.
• [x] I have read the FAQs inside the app (Menu -> About -> FAQs) and my problem isn't listed.
• [x] I have taken the time to fill in all the required details. I understand that the request will be dismissed otherwise.
• [x] This issue contains only one feature request.
• [x] I have read and understood the contribution guidelines.

Feature description

A way to preview images when the destination expects a single file

Why do you want this feature?

Some files are in aspect ratios which makes it very hard to know the full image in the thumbnail. When the destination expects only a single file, long pressing on an image immediately selects it and exits out of the file picker. The default android file picker has a button on top of the Image to preview it but Gallery does not.

Additional information

No response

[naveensingh]

Related: https://github.com/FossifyOrg/Gallery/issues/210