Check for multiple api & types instances (#797)

packages/types/package.json

@@ -30,7 +30,7 @@
   "homepage": "https://github.com/polkadot-js/api/tree/master/packages/types#readme",
   "dependencies": {
     "@babel/runtime": "^7.4.0",
-    "@polkadot/keyring": "^0.41.1",
-    "@polkadot/util": "^0.41.1"
+    "@polkadot/keyring": "^0.42.0-beta.0",
+    "@polkadot/util": "^0.42.0-beta.0"
   }
 }

packages/types/src/index.ts

@@ -5,5 +5,9 @@
 // NOTE When adding any types here, we need to update the coumentation links as
 // well - <root>/docs/SUMMARY.md as well as ../README.md
 
+import { assertSingletonPackage } from '@polkadot/util';
+
+assertSingletonPackage('@polkadot/types');
+
 export * from './codec';
 export * from './index.types';