Add Terms of use and Privacy links to website footer. (#436)

Summary:
Now required for OSS projects: T66558196

Pull Request resolved: #436

Test Plan:
local build:
{F236256079}

Reviewed By: sdaulton

Differential Revision: D21404513

Pulled By: Balandat

fbshipit-source-id: 794a9d5158ff418e13b36062316a3d4cbde87444

Author: Balandat

website/core/Footer.js

@@ -74,6 +74,21 @@ class Footer extends React.Component {
             <a href={`${this.props.config.baseUrl}tutorials/`}>Tutorials</a>
             <a href={`${this.props.config.baseUrl}api/`}>API Reference</a>
           </div>
+          <div className="footerSection">
+            <h5>Legal</h5>
+            <a
+              href="https://opensource.facebook.com/legal/privacy/"
+              target="_blank"
+              rel="noreferrer noopener">
+              Privacy
+            </a>
+            <a
+              href="https://opensource.facebook.com/legal/terms/"
+              target="_blank"
+              rel="noreferrer noopener">
+              Terms
+            </a>
+          </div>
           <SocialFooter config={this.props.config} />
         </section>
         <a