Add Governor contracts (#2672)

Co-authored-by: Francisco Giordano <frangio.1@gmail.com>

test/helpers/enums.js

@@ -0,0 +1,24 @@
+const { BN } = require('@openzeppelin/test-helpers');
+
+function Enum (...options) {
+  return Object.fromEntries(options.map((key, i) => [ key, new BN(i) ]));
+}
+
+module.exports = {
+  Enum,
+  ProposalState: Enum(
+    'Pending',
+    'Active',
+    'Canceled',
+    'Defeated',
+    'Succeeded',
+    'Queued',
+    'Expired',
+    'Executed',
+  ),
+  VoteType: Enum(
+    'Against',
+    'For',
+    'Abstain',
+  ),
+};