Fix .gitignore: stop tracking ignored files

backend/lib/openzeppelin-contracts/test/utils/escrow/Escrow.test.js

@@ -0,0 +1,14 @@
+require('@openzeppelin/test-helpers');
+const { shouldBehaveLikeEscrow } = require('./Escrow.behavior');
+
+const Escrow = artifacts.require('Escrow');
+
+contract('Escrow', function (accounts) {
+  const [owner, ...otherAccounts] = accounts;
+
+  beforeEach(async function () {
+    this.escrow = await Escrow.new({ from: owner });
+  });
+
+  shouldBehaveLikeEscrow(owner, otherAccounts);
+});