Update gitignore (sorry)

electron/node_modules/global-agent/src/errors.js

@@ -0,0 +1,15 @@
+// @flow
+
+/* eslint-disable fp/no-class, fp/no-this */
+
+import ExtendableError from 'es6-error';
+
+export class UnexpectedStateError extends ExtendableError {
+  code: string;
+
+  constructor (message: string, code: string = 'UNEXPECTED_STATE_ERROR') {
+    super(message);
+
+    this.code = code;
+  }
+}