Update README.md (#21)

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Author: toshimaru

README.md

@@ -1,3 +1,26 @@
 # [railsdoc.github.io](https://railsdoc.github.io/) 
 
 [![Build Status](https://travis-ci.com/railsdoc/railsdoc.github.io.svg?branch=page-source)](https://travis-ci.com/railsdoc/railsdoc.github.io)
+
+railsdoc.github.io is yet another Rails API documentation website.
+
+## Project Goal
+
+The project goal is **making [api.rubyonrails.org](https://api.rubyonrails.org/) SEO-friendly**.
+
+### Additional Goals
+
+Thare are some enhancements in addition to SEO.
+
+- [x] Built by [Jekyll](https://github.com/jekyll/jekyll)
+- [x] Styled by [bootstrap(v4)](https://github.com/twbs/bootstrap)
+- [x] No iframe layout
+- [x] Table of Contents
+- [x] Google Custom Search
+- [ ] Mobile-friendly design
+- [ ] Multiple version documentation
+- [ ] etc. (see. https://github.com/railsdoc/railsdoc.github.io/issues)
+
+## Feature Request  
+
+Please create an [issue](https://github.com/railsdoc/railsdoc.github.io/issues).