Update gitignore (sorry)

electron/node_modules/electron-is-dev/index.d.ts

@@ -0,0 +1,21 @@
+/**
+Check if [Electron](https://electronjs.org) is running in development.
+
+This package must be used from the Electron main process.
+
+You can force development mode by setting the `ELECTRON_IS_DEV` environment variable to `1`.
+
+@example
+```
+import isDev = require('electron-is-dev');
+
+if (isDev) {
+	console.log('Running in development');
+} else {
+	console.log('Running in production');
+}
+```
+*/
+declare const electronIsDev: boolean;
+
+export = electronIsDev;