Add more details to the Module Structure (#1048)

See discussion here
electron-react-boilerplate/electron-react-boilerplate#1042 (comment)

README.md

@@ -191,14 +191,34 @@ $ npm run test-e2e
 
 See [electron-builder CLI Usage](https://github.com/electron-userland/electron-builder#cli-usage)
 
-#### Module Structure
+## How to add modules to the project
 
-This boilerplate uses a [two package.json structure](https://github.com/electron-userland/electron-builder/wiki/Two-package.json-Structure). For an example app that uses this boilerplate and packages native dependencies, see [erb-sqlite-example](https://github.com/amilajack/erb-sqlite-example).
+You will need to add other modules to this boilerplate, depending on the requirements of your project. For example, you may want to add [node-postgres](https://github.com/brianc/node-postgres) to communicate with PostgreSQL database, or 
+[material-ui](http://www.material-ui.com/) to reuse react UI components.
 
-1. If the module is native to a platform or otherwise should be included with the published package (i.e. bcrypt, openbci), it should be listed under `dependencies` in `./app/package.json`.
-2. If a module is `import`ed by another module, include it in `dependencies` in `./package.json`.   See [this ESLint rule](https://github.com/benmosher/eslint-plugin-import/blob/master/docs/rules/no-extraneous-dependencies.md).
+⚠️ Please read following section before installing any dependencies ⚠️
+
+### Module Structure
+
+This boilerplate uses a [two package.json structure](https://github.com/electron-userland/electron-builder/wiki/Two-package.json-Structure). This means, you will have two `package.json` files.
+
+1. `./package.json` in the root of your project
+1. `./app/package.json` inside `app` folder
+
+### Which `package.json` file to use
+
+**Rule of thumb** is: all modules go into `./package.json` except native modules. Native modules go into `./app/package.json`.
+
+1. If the module is native to a platform (like node-postgres) or otherwise should be included with the published package (i.e. bcrypt, openbci), it should be listed under `dependencies` in `./app/package.json`.
+2. If a module is `import`ed by another module, include it in `dependencies` in `./package.json`.   See [this ESLint rule](https://github.com/benmosher/eslint-plugin-import/blob/master/docs/rules/no-extraneous-dependencies.md). Examples of such modules are `material-ui`, `redux-form`, and `moment`.
 3. Otherwise, modules used for building, testing and debugging should be included in `devDependencies` in `./package.json`.
 
+### Further Readings
+
+See the wiki page, [Module Structure — Two package.json Structure](https://github.com/chentsulin/electron-react-boilerplate/wiki/Module-Structure----Two-package.json-Structure) to understand what is native module, the rationale behind two package.json structure and more.
+
+For an example app that uses this boilerplate and packages native dependencies, see [erb-sqlite-example](https://github.com/amilajack/erb-sqlite-example).
+
 ## Static Type Checking
 This project comes with Flow support out of the box! You can annotate your code with types, [get Flow errors as ESLint errors](https://github.com/amilajack/eslint-plugin-flowtype-errors), and get [type errors during runtime](https://github.com/codemix/flow-runtime) during development. Types are completely optional.