match the footer font style to the header (#498)

With this change both the header and the footer use sans-serif which
looks more consistent in a page with a serif body.

Co-authored-by: Luiz F. A. de Prá <luizdepra@users.noreply.github.com>

assets/scss/_footer.scss

@@ -1,6 +1,7 @@
 .footer {
   width: 100%;
   text-align: center;
+  font-family: $heading-font-family;
   line-height: 2.0rem;
   margin-bottom:1.0rem;
   a {

resources/_gen/assets/scss/scss/coder.scss_5e1eb8e37c42cdfb6215b61e44dcfa5f.json

@@ -1 +1 @@
-{"Target":"css/coder.min.b79ffb503467976bb5db1a55f11d2db1d230f6a68dc7aa55cf08be4f048cb1b8.css","MediaType":"text/css","Data":{"Integrity":"sha256-t5/7UDRnl2u12xpV8R0tsdIw9qaNx6pVzwi+TwSMsbg="}}
+{"Target":"css/coder.min.b79ffb503467976bb5db1a55f11d2db1d230f6a68dc7aa55cf08be4f048cb1b8.css","MediaType":"text/css","Data":{"Integrity":"sha256-t5/7UDRnl2u12xpV8R0tsdIw9qaNx6pVzwi+TwSMsbg="}}