Update mobile navigation to a hamburger menu and update link hierarchy

[madcampos]

At events when we direct people to go to Toronto JS website, they usually are looking for links to join slack and how to volunteer.

The issue is that on mobile the links show only as icons and it is not very intuitive for users what icon does what, so we could benefit for another type of navigation, like a hamburger menu that shows text alongside with the icons.

Also, to make it easier to users to navigate, we should reorganize the links so the most used ones are first on the menu.