feat: add new marketplace and keep the old one as legacy (#37)

BREAKING CHANGE: the abi for the Marketplace contract changed

src/contracts/LegacyMarketplace.ts

@@ -0,0 +1,16 @@
+import { Contract } from '../ethereum'
+import { fulfillContractMethods } from './verification'
+
+const { abi } = require('./artifacts/LegacyMarketplace.json')
+
+/** LegacyMarketplace contract class */
+export class LegacyMarketplace extends Contract {
+  constructor(address: string) {
+    super(address, abi)
+    fulfillContractMethods(this, abi)
+  }
+
+  getContractName() {
+    return 'LegacyMarketplace'
+  }
+}