Add notes on how to set up a custom folder for storing photos

[saberraz]

MerginMaps/mobile#1575 (comment)

[wonder-sk]

Currently there are two places where the configuration of paths to images is documented:

• https://help.inputapp.io/howto/settingup_forms_photos
• https://help.inputapp.io/howto/project_config

1. The detailed docs from "project_config" page should rather go to the "settingup_forms_photos" page.
2. It should be made clear in how to configure the widget (with a screenshot) to avoid the user error in Custom folder for storing photos no longer works MerginMaps/mobile#1575

[PeterPetrik]

can you make also pull request here? https://github.com/MerginMaps/docs
this repo will be soon deprecated . thanks