Add an alert for successful role update

templates/workspace_members.html

@@ -33,6 +33,18 @@
   ) }}
 {% endif %}
 
+{% set updated_member_name = request.args.get("memberName") %}
+{% if updated_member_name %}
+    {% set message -%}
+      <p>{{ updated_member_name }}'s role  was successfully updated.</p>
+    {%- endset %}
+
+  {{ Alert('Workspace role updated successfully',
+    message=message,
+    level='success'
+  ) }}
+{% endif %}
+
   <form class='search-bar'>
     <div class='usa-input search-input'>
       <label for='members-search'>Search members by name</label>