[Mobile] Sidenav to cover all the space

[german-e-mas]

Related to #6

Make the sidenav as wide as the screen on Mobile devices.

Check the feasibility of this:

• The hamburguer icon should transform to a cancel and be on top of the expanded sidenav as well.
• We shouldn't be able to scroll horizontally while the sidenav is open. It should be an overlay.

In case it is very difficult to implement this in the current theme, perhaps it's a good idea to leave the current behavior. FYI @mjeronimo . I'll let you know how this goes.

[mjeronimo]

Yes, it's OK to leave as-is if it seems like a lot of work. A related thing is that the hamburger sometimes doesn't show up because of the background image color (black on black). Any way to adapt to the background image color?

[german-e-mas]

While the sidenav width can be changed on mobile views, the button position is problematic.

Given the way the icon is built, it will be very complicated to come up with a solution for it to look good in this case.

I think the width can be left as it currently is. PR mjeronimo/pelican-fh5co-marble#6 solves it's color issue.

Let me know what do you think @mjeronimo

[mjeronimo]

Sounds good to me. We can close this one.

[german-e-mas]

mjeronimo/pelican-fh5co-marble#6 has been merged. I'll proceed to close this one!