Add Fira Sans Mono font

sass/_base.scss

@@ -1,5 +1,6 @@
 $light-fonts: "Fira Sans Light", sans-serif;
 $normal-fonts: "Fira Sans", sans-serif;
+$mono-fonts: "Fira Mono", monospace;
 $page-width: 800px;
 $primary-color: #333;
 $bg-color: #eee;
@@ -33,6 +34,12 @@ html {
     font-weight: 400;
     src: local("Fira Sans"), local("FiraSans-Regular"), url("fonts/Fira Sans.woff2") format("woff2");
 }
+@font-face {
+    font-family: "Fira Mono";
+    font-style: normal;
+    font-weight: 400;
+    src: local("Fira Mono"), local("FiraMono-Regular"), url("fonts/FiraMono-Regular.woff2") format("woff2");
+}
 body {
     max-width: $page-width;
     margin: auto;
@@ -137,3 +144,7 @@ nav {
     float: left;
   }
 }
+code {
+  font-family: $mono-fonts;
+  font-size:14px;
+}