Use fonts found on terminals for the web config.

Instead of just using Courier New across the board, have the
browser try several likely available fonts before defaulting
to the system's "monospace".

Thanks @MarkGriffiths
Fixes #2924

share/tools/web_config/fishconfig.css

@@ -1,6 +1,6 @@
 body {
     background-color: #292929;
-    font-family: Courier, "Courier New", monospace;
+    font-family: "Source Code Pro", "DejaVu Sans Mono", Menlo, "Ubuntu Mono", Consolas, Monaco, "Lucida Console", monospace, fixed;
     color: white;
 }