Add Header Link to FreeTube docs

[ChunkyProgrammer]

Links to docs is missing from header

[efb4f5ff-1298-471a-8973-3d47447115dc]

file that needs to be edited can be found here:

https://github.com/FreeTubeApp/FreeTubeApp.io/blob/master/src/includes/header.php

[efb4f5ff-1298-471a-8973-3d47447115dc]

Tried to do this thinking it was a simple change but the whole layout of the website broke. I think our css is cursed