fallback to 'monospace' for code font-family (#1674)

Some people like myself disable custom fonts on the web. The reasons
are often related to accesibility. In my case it is dyslexia, but
there are probably other vision related reasons too.

Signed-off-by: Christopher Bayliss <cjbdev@icloud.com>

Author: cjbayliss

_sass/components/code.scss

@@ -174,7 +174,7 @@
     code {
         // style that would be injected by hljs when JS is enabled
         display: block;
-        font-family: 'Consolas';
+        font-family: 'Consolas', monospace;
         border: none;
         display: block;
         overflow-x: auto;

_sass/layout/type-md.scss

@@ -151,7 +151,7 @@
     li,
     p {
         code {
-            font-family: 'Consolas';
+            font-family: 'Consolas', monospace;
             background-color: #fff;
             color: #859900;
             @include border-radius($border-radius-medium);