Signup form on all mobile pages

[MirandaEcho]

We need an estimate for what it would take to add a signup form to all mobile pages on the site. This could be in the mobile nav, adding a section to the top that only displays on mobile, etc. We can discuss at scrum if needed, otherwise please add thoughts on an estimate here. Thanks!

[benlk]

A newsletter signup form already exists on most pages on the site, in the main sidebar. However, this form is currently hidden from view on mobile, as seen on https://energynews.us/digests/natural-gas-bans-draw-skepticism-from-utility-regulators/ and https://energynews.us/2020/02/11/west/colorado-legislators-take-up-proposal-for-renewable-natural-gas-standard/

What we could do is put the newsletter signup form back at the start of articles. We did this before (and removed it in #68 because the form was the wrong form). If we were to take this same approach, we'd want to, instead of putting a widget directly at the top of articles, create an "Article Top" widget area to match "Article Bottom", and output that widget area at the top of the article.

Combined with making sure that the newsletter signup form output at the top of articles looks good, I think this might take 2-4h?

[benlk]

the idea is to have a form at the very top of all pages on mobile

We can use the "Header Ad Zone" widget area. Improvements to styling, once we know what signup form we're using, would take up to two hours.

Here's what the current "ENN Mailchimp Signup" widget looks like in the "Header Ad Zone" widget area on article pages:

It has a slightly different appearance on term archives and the homepage:

[MirandaEcho]

We have approval from Ken to proceed with this for an additional two hours, so I'll update it when I update the rest of the issues.

[benlk]

Config:

• add widget to widget area
• set widget to only show on mobile

Dev:

• consistency of styles

Admin:

• add note to the deployment issue

[benlk]

PR #88 now ready for review.