Add an option to disable the image resizing prompt

[laurent22]

Add an option in the configuration screen under the "Note" section.

It should be a dropdown with label "Image resizing". The options should be "Always ask", "Always resize", "Never resize".

Depending on this option, either prompt the user when attaching an image, or always resize, or never resize.

To the existing message "You are about to attach a large image (%dx%d pixels). Would you like to resize it down to %d pixels before attaching it?", add some information string: "(You may change this default behaviour in the options)".

It needs to work on desktop and mobile.