regal: Add client flags for custom features

We are using the 'experimental' feature flagging option
in init options for Regal to signal what it can do.

open-policy-agent/regal#1867 This is the client
side of the same for the client to show what it can do.

Signed-off-by: Charlie Egan <charlie_egan@apple.com>

Author: charlieegan3

package.json

@@ -365,4 +365,4 @@
     "publisherDisplayName": "Torin Sandall",
     "publisherId": "4052f3dc-ff54-4c3b-9ad2-44e7ac5b9f4d"
   }
-}
+}