Refresh: Add CTA pencil banner

[reemhamz]

One-line summary

This pencil banner, which is to be added to all the pages that'll be using the new navigation (https://github.com/mozilla/bedrock/pull/14966), will be replacing the nav CTAs we currently have on www.mozilla.org.

This is currently a WIP 'til the new nav PR gets merged. The placements of files and imports will be updated and refined then, as well. For now, I just did what I could to get the banner showing, which will hopefully reduce whatever integration we need to get done until the new nav descends upon us ✨

[!NOTE] Going forward with this banner without the Download Firefox alternative + logic

Issue / Bugzilla link

Fixes https://github.com/mozilla/bedrock/issues/15095

Testing

Make sure your your local waffle config has the following: (P.S. new docs here https://bedrock.readthedocs.io/en/latest/install.html#testing)

M24_HOME = on
M24_ABOUT = on
M24_NAVIGATION_AND_FOOTER = on

http://localhost:8000/en-US/