Add pysa logo to documentation

Summary: We had a pysa logo for a while, but we never actually put it on our website. Let's do that.

Reviewed By: anwesht

Differential Revision: D86572903

fbshipit-source-id: 0cc096a11bf3c4b1a21ca66b3a4354776b673c89

Author: arthaud

documentation/website/docs/pysa_basics.md

@@ -1,11 +1,14 @@
 ---
 id: pysa-basics
-title: Pysa Overview
+title: Pysa (Static Analysis for Security)
 sidebar_label: Overview
 ---
 
 import Internal from './fb/pysa_basics_internal.md';
 import YouTube from 'react-youtube';
+import useBaseUrl from '@docusaurus/useBaseUrl';
+
+<img alt="Pysa Logo" style={{width: '400px'}} src={useBaseUrl('img/pysa.png')} />
 
 Pyre has applications beyond type checking python code: it can also run static
 analysis, more specifically called **Taint Analysis**, to identify potential security issues.