docs(readme): updates API docs references to v3

Author: bkrem

README.md

@@ -26,14 +26,14 @@
 
 <p align="center">
   <h3 align="center"><a href="https://bkrem.github.io/react-d3-tree">👾 Playground</a></h3>
-  <h3 align="center"><a href="https://bkrem.github.io/react-d3-tree/docs">📖 API Documentation (v2)</a></h3>
+  <h3 align="center"><a href="https://bkrem.github.io/react-d3-tree/docs">📖 API Documentation (v3)</a></h3>
 </p>
 
 React D3 Tree is a [React](http://facebook.github.io/react/) component that lets you represent hierarchical data (e.g. family trees, org charts, file directories) as an interactive tree graph with minimal setup, by leveraging [D3](https://d3js.org/)'s `tree` layout.
 
-> **Want to see what's changed in v2? Check out the [v2 release notes](https://github.com/bkrem/react-d3-tree/releases/tag/v2.0.0).**
+> **Upgrading from v1? Check out the [v2 release notes](https://github.com/bkrem/react-d3-tree/releases/tag/v2.0.0).**
 
-> **Looking for v1? Click [here](https://github.com/bkrem/react-d3-tree/tree/v1).**
+> **[Legacy v1 docs](https://github.com/bkrem/react-d3-tree/tree/v1)**
 
 ## Contents <!-- omit in toc -->
 - [Installation](#installation)

demo/src/App.js

@@ -245,7 +245,7 @@ class App extends Component {
                     <span role="img" aria-label="open book emoji">
                       📖
                     </span>{' '}
-                    API Docs (v2)
+                    API Docs (v3)
                   </a>
                 </h3>
                 <h4 className="prop">Examples</h4>