Add links to Support credit line

Addresses #23

_includes/footer.html

@@ -25,4 +25,4 @@
  <a rel="license" href="http://creativecommons.org/publicdomain/zero/1.0/">
  <img src="https://licensebuttons.net/p/zero/1.0/80x15.png" style="border-style: none;" alt="CC0" />
  </a>
- {{ site.name | default: site.title }}. {{ site.data.ui-text[site.locale].powered_by }} <a href="http://jekyllrb.com" rel="nofollow">Jekyll</a> &amp; <a href="https://mademistakes.com/work/minimal-mistakes-jekyll-theme/" rel="nofollow">Minimal Mistakes</a>. Supported by the National Park Service and National Conference of State Historic Preservation Officers.</div>
+ {{ site.name | default: site.title }}. {{ site.data.ui-text[site.locale].powered_by }} <a href="http://jekyllrb.com" rel="nofollow">Jekyll</a> &amp; <a href="https://mademistakes.com/work/minimal-mistakes-jekyll-theme/" rel="nofollow">Minimal Mistakes</a>.<br/>Supported by the <a href="https://www.nps.gov/" rel="nofollow">National Park Service</a> and <a href="http://ncshpo.org/" rel="nofollow">National Conference of State Historic Preservation Officers</a>.</div>