Frontent build system is ready (#3)

* Frontent build system is ready

* Set up linter for frontend part

* move code to /src

* update db

* upd test

* remove db

* ignore .db

src/frontend/js/app.js

@@ -0,0 +1,12 @@
+// No inspection for unused var `css` because it's used for css bundle
+// eslint-disable-next-line no-unused-vars
+import css from '../styles/main.pcss';
+
+module.exports = class Docs {
+  /**
+   * @constructor
+   */
+  constructor() {
+    console.log('CodeX Docs initialized');
+  }
+};