Add MaxCDN

The enterprise side of MaxCDN used to be named NetDNA, and it’s still
what they use in their headers. Look at www.canvas.be for an example
of a full website going through MaxCDN.

src/apps.json

@@ -4019,6 +4019,16 @@
       "website": "mathjax.org",
       "icon": "MathJax.png"
     },
+    "MaxCDN": {
+      "cats": [
+        31
+      ],
+      "headers": {
+        "Server": "NetDNA"
+      },
+      "website": "www.maxcdn.com",
+      "icon": "MaxCDN.png"
+    },
     "MaxSite CMS": {
       "cats": [
         1