Move community link into a separate menu

[nabaco]

I'm opening the issue to not forget. I want to move all the community related links in the top menu to a separate sub menu. Will need to look into bootstrap documentation to see how to do it.

• Forums
• Gitter
• Gallery
• Wiki?
• News?

Additionally I will need to add a new link to contribute on OC. Maybe a button on the top menubar,
and something bigger on the footer that is on each page.

It requires me to work on the other box, where I can stage the website locally, so it'll take me some time.

[nabaco]

For the OC buttons: https://docs.opencollective.com/help/collectives/widgets