[2.3.0] add customizable template infos to `PROJECT_CONTACT` feature

[MyPyDavid]

Some extra info about the template can be added to this paragraph:

• https://rdmo.readthedocs.io/en/latest/configuration/projects.html#project-contact-form
• https://github.com/rdmorganiser/rdmo/blob/main/rdmo/projects/templates/projects/project_interview_contact_help.html