Include documentation on website and utils.

app/README.md

@@ -1,3 +1,5 @@
+This directory contains the source code of the Mind Expanding Books [website](https://books.vishnuks.com)
+
 ## How to setup development environment
 
 ```bash
@@ -6,3 +8,16 @@ cd app/
 npm install
 gatsby develop
 ```
+
+## High level overview of the website
+
+- The website is made using Gatsby, which is a React based static site generator.
+- The website is deployed in Netlify automatically whenever a commit is pushed to GitHub.
+- When you create a pull request with changes to the source code, Netlify will automatically
+  create a website for previewing the changes. You can click on "Details" in the "Deploy preview ready!"
+  message in the pull request page for seeing the website.
+
+## From where does the website fetches the data of the books?
+
+Website fetches the data of the books from `app/src/book.json` file. See [README in utils directory](../utils/README.MD)
+for details on how this file is generated.