Fix .gitignore: stop tracking ignored files

backend/lib/openzeppelin-contracts/scripts/release/synchronize-versions.js

@@ -0,0 +1,15 @@
+#!/usr/bin/env node
+
+// Synchronizes the version in contracts/package.json with the one in package.json.
+// This is run automatically when npm version is run.
+
+const fs = require('fs');
+
+setVersion('package.json', 'contracts/package.json');
+
+function setVersion(from, to) {
+  const fromJson = JSON.parse(fs.readFileSync(from));
+  const toJson = JSON.parse(fs.readFileSync(to));
+  toJson.version = fromJson.version;
+  fs.writeFileSync(to, JSON.stringify(toJson, null, 2) + '\n');
+}