Add link to new mapping tool to candidate and referendum pages

[anlawyer]

Suzanne has been working with Socrata on a sweet new tool for showing maps (and other cool visualizations) of contributions to candidates and referendums. She'll be adding the links to the new site for each candidate to our main spreadsheet soon.

Please add a link to this new site on each candidate/referendum page under the section where we show the breakdown of contributions by location. From Suzanne: "Maybe some kind of an icon to indicate a map and the link could say "Show me the money" or "Contributor map", something like that."

[anlawyer]

Can download the svg file from here: https://fontawesome.com/icons/map-marked-alt?style=solid

[anlawyer]

The field name coming from the backend is map_url. PR here: https://github.com/caciviclab/disclosure-backend-static/pull/278/files