Fixes #5706 - Adds Dai/Sai to currency display (#7986)

With the change from infura to cryptocompare https://github.com/MetaMask/gaba/pull/30/files#diff-50c3c47cc5fa12e5213a6cc900476f41L41-R48 we have numerous conversion rates to go through and add if we like to.

ui/app/helpers/constants/available-conversions.json

@@ -238,5 +238,13 @@
   {
     "code": "zec",
     "name": "Zcash"
+  },
+  {
+    "code": "dai",
+    "name": "DAI"
+  },
+  {
+    "code": "sai",
+    "name": "SAI"
   }
 ]