BO37 - Create a page to provide informations about the conference's venue

[gregoriopalama]

Create a page that will use the BackOfficeLayout.

The link in the drawer menu should be "Venue". For the icon we will use material design icons and the icon location on.

The page's layout should be as following:

The page will provide a form, with the possibility to add all kind of informations about the venue:

• name, required, is the name of the venue, or how to search for it on Maps;
• address, required, should be the complete address;
• latitude and longitude: both required, should not be editable. The map will be used to populate them. When the Organizer insert the address, a reverse geocoding request will be done, to get the latitude and longitude. The marker in the map will be movable, to allow the user to manually pick a different position if more precision is needed;
• mapId, optional. This is the mapId that we can get from GCP when we configure a map style and assign it to a map. This will allow the Maps API to automatically stylize the map with the configured map style;
• description, optional. For this field, markdown should be allowed. We might use a markdown editor here;
• marker, optional. The image to use for the marker. If provided, it will be uploaded to Firebase Storage. Also, if already provided, the form should allow the user to delete it or to update it.

Depends on #200 and #201.