Create the 'button' for mobile for the 'call for maps'

[DaniDaubaras]

Currently appears only in the dropdown, create the button for it. Similar to the ticketing button - specifically missing on mobile

[jbelien]

Hey @DaniDaubaras,

There is no enough room to put the 2 buttons in the header ; see discussion in PR #119.

@nobohan put the "Submit your maps" button on the homepage, right above the "Sponsors" section.