Create Newsletter and add a link to it in the footer

**Is your feature request related to a problem? Please describe.**
We need to update the public and stakeholders as new features are created and we do more things in the community: a newsletter is a great avenue for that as many service providers and people who are interested in reentry use their email primarily over social networks.

**Describe the solution you'd like**
1) Create a mailchimp or alternative newsletter service, not sure how to do this collaboratively, but I @paul-rinaldi needs admin rights or close to that on there
2) Replace this line below in ```footer/index.js``` with the statement Subscribe to our Newsletter for Updates! with a link to the mailchimp sign up/subscribe link (a/href).

**Describe alternatives you've considered**
I haven't considered an alternatives but maybe you know of great ways to communicate about community project / civic tech progress to the community using it? Twitter? @Aycrazy

**Additional context**
See above. I (@paul-rinaldi ) may ask the MSOE honors freshman class to do this.

Beginne mit dem Lesen von footer/index.js und identifiziere die aktuelle Footer-Zeile, die im Issue angezeigt wird. Legt gemeinsam einen Newsletter-Dienst fest und ersetzt dann diese Zeile durch den angeforderten Anmeldetext und Link; fertig ist es, wenn der Footer-Link zur Newsletter-Anmeldeseite führt und der Zugang zum Dienst eingerichtet ist.

Vom Indexierungsmodell aus dem Issue-Text verfasst.