Add 2021 User Survey link to index.html

Author: GenevieveBuckley

index.html

@@ -105,6 +105,13 @@
 
           <div class="container marketing p-md-5">
 
+            <div class="alert alert-warning alert-dismissible fade show" role="alert" style="text-align: center;font-size: 1.1em;max-width: 720px;margin-left: auto;margin-right: auto;">
+                Help inform future development and improve the Dask community experience - take the <a href="https://forms.gle/F7QSGpSHwBWu8NCg8">2021 Dask User Survey</a>
+              <button type="button" class="close" data-dismiss="alert" aria-label="Close">
+                <span aria-hidden="true">&times;</span>
+              </button>
+            </div>
+            
             <!-- Three columns of text below the carousel -->
             <h2 class="featurette-heading">Integrates with existing projects</h2>
             <h2 class="featurette-subheading">Built with the broader community</h2>