Enable audio/webaudio Modernizr rule

Signed-off-by: Michael Telatynski <7t3chguy@gmail.com>

.modernizr.json

@@ -31,6 +31,7 @@
         "test/json",
         "test/network/fetch",
         "test/storage/localstorage",
-        "test/window/resizeobserver"
+        "test/window/resizeobserver",
+        "test/audio/webaudio"
     ]
 }