fix: allow immutable@^4.0.0-rc

Author: jedwards1211

package.json

@@ -84,7 +84,7 @@
     "lodash.size": "^4.2.0"
   },
   "peerDependencies": {
-    "immutable": "^3.8.1 || ^4.0.0",
+    "immutable": "^3.8.1 || ^4.0.0 || ^4.0.0-rc",
     "mindfront-redux-utils": "^1.2.3"
   },
   "pre-commit": [