Add repo social preview

I have added github social preview images in the readme file.

I learned, you can align paragraph, images or heading using html in markdown file.

Author: gauravkukade

README.md

@@ -1,4 +1,8 @@
-# codeRolls blog
+<p align="center">
+![coderolls GitHub Repo](/github-repo-social-preview.png)
+</p>
+
+<center> <h1>codeRolls blog</h1> </center>
 
 [Live Demo](https://coderolls.github.io)
 
@@ -9,6 +13,6 @@ Copyright (C) 2019 codeRolls, https://codeRolls.com
 
 CodeRolls is a blog about java programming language and related technologies. All post are copyright property of Guarva Kukade (@gauravkukade). If you want to read the blog post please visit coderolls.com
 
-You should not copy these blogpost, you should right your own. 🙂
+You can not copy these blogposts, you should right your own. 🙂
 
 Thank you!