docs: Add docs about how to manually load app deps (electron-userland…

…#473)

docs/Loading App Dependencies Manually.md

@@ -0,0 +1,20 @@
+> Important: This approach must be used only in development environment.
+> Since the release version of your application the `app` directory should self contain all used files.
+
+In case on development environment your app runs the main process (executed by electron) not inside the `/app` folder. You may need to load the `/app` dependencies manually. Because the app dependencies are be placed at `/app/node_modules` and your main process that is running in a different directory will not have access by default to that directory.
+
+Instead of duplicating the app dependencies in the development `package.json` it is possible to make the electron main process load the app dependencies manually with an approach like this:
+
+```js
+// Given this file is: /src/browser/main.js
+
+var path = require('path');
+
+var devMode = (process.argv || []).indexOf('--dev') !== -1;
+
+if (devMode) {
+  // load the app dependencies
+  var PATH_APP_NODE_MODULES = path.join(__dirname, '..', '..', 'app', 'node_modules');
+  require('module').globalPaths.push(PATH_APP_NODE_MODULES);
+}
+```