Add ui-util formatting & util (#76)

* Add ui-util formatting & util

* Update README

packages/ui-util/src/isTestChain.ts

@@ -0,0 +1,13 @@
+// Copyright 2017-2019 @polkadot/ui-util authors & contributors
+// This software may be modified and distributed under the terms
+// of the Apache-2.0 license. See the LICENSE file for details.
+
+const re = new RegExp('^(Development|Local Testnet)$');
+
+export default function isTestChain (chain?: string | null): boolean {
+  if (!chain) {
+    return false;
+  }
+
+  return !!re.test(chain.toString());
+}