docs: add social banner in support of Ukraine (#4396)

* Adding eli5 video

* Adding social banner

* fixing lint errors

* moving style into the template

website/templates/home.html

@@ -1,3 +1,12 @@
+<div  style="padding: 0 0; background-color: #000;">
+    <div style="   font-weight: bold; font-size: 20px; padding: 20px; max-width: 768px; margin: 0 auto; text-align: center; color: white;">
+      Support Ukraine 🇺🇦 
+      <a href="https://opensource.fb.com/support-ukraine">
+        Help Provide Humanitarian Aid to Ukraine
+      </a>
+      .
+    </div>
+</div>
 <div class="jumbotron" style="background-color: #ec1454; margin-bottom: 0px">
     <div class="container" style="text-align: center; color: #fff">
         <h1 style="font-size: 40px; margin-bottom: 30px; margin-top: 32px; letter-spacing: -0.01em;