exif sample project

[alex-cit]

Exif metadata refers to lutraconsulting/test_exif project. This project should be moved to "documentation".

Default values used in this project (using read_exif() function) display an error - the function is not known.

[PeterPetrik]

isn't read_exif function only available on Input App? in that case I am not sure of preview on desktop would work, since QGIS desktop may know know about it (@wonder-sk ?) if that is the case, it is not an error, but we can warn user that this is perfectly ok