Add @matt-gadd as a contributor

Author: CompuIves

.all-contributorsrc

@@ -923,6 +923,15 @@
       "contributions": [
         "code"
       ]
+    },
+    {
+      "login": "matt-gadd",
+      "name": "Matthew Gadd",
+      "avatar_url": "https://avatars0.githubusercontent.com/u/2183490?v=4",
+      "profile": "https://github.com/matt-gadd",
+      "contributions": [
+        "code"
+      ]
     }
   ],
   "repoType": "github"