Allow to type a latlng in the search box

[yohanboniface]

When entering a string in a form of a latlng, we'll do two things:

• add a result that allow to center the map on this latlng (and to create a new point if edit mode is enabled)
• do a reverse search and display it result if any

fix #1000
cf #1001

[davidbgk]

This is one of these advanced feature that are hard to discover, maybe doable with an explicit label: Search a place name (or coordinates)?

[brunetton]

Thank you ! Can't wait to use it in production 🥳