Add custom external pages
Add an option in admin panel to add external pages.
What should be possible:
- create a new page
- give a name to this page (translation not managed for now)
- give a URL to this page
Result: a new page should be inserted to the menu (to be tested on computer and on mobile) and send the user to the external page (opens in a new tab)

Examples on how it can be used:
- page "FAQ"--
- page "subscribe to our newsletter"
- page "city" (such as in https://mobilisons.ch/)
Edited by Lahax