Warn users not to use disallowed characters in photo naming #680

Files with special characters are forbidden to be synced.
The app sanitizes these characters to allow the sync.
We include good examples in the dedicated docs page but we could add an information about disallowed characters.
It's these :|?*"

https://merginmaps.com/docs/gis/photo-names/#how-to-set-photo-names-format

Related to PR that adds preview warning MerginMaps/qgis-plugin#810 and issue MerginMaps/qgis-plugin#678