Add database engine form (#3307)

Author: kyleconroy

docs/_templates/breadcrumbs.html

@@ -3,7 +3,7 @@
 {% block breadcrumbs %}
 {% if show_banner %}
 <header id="banner">
-  <div>Introducing <a href="https://sqlc.dev/posts/2023/12/04/preview-typescript-support-with-sqlc-gen-typescript/">sqlc-gen-typescript</a>: Generate TypeScript from SQL.</div>
+  <div>Join the wait list for <a href="https://bm2gstcnhch.typeform.com/to/fV96Dsyf">BigQuery</a>, <a href="https://bm2gstcnhch.typeform.com/to/fV96Dsyf">ClickHouse</a>, <a href="https://bm2gstcnhch.typeform.com/to/fV96Dsyf">MSSQL</a>, or <a href="https://bm2gstcnhch.typeform.com/to/fV96Dsyf">Spanner</a> today.</div>
 </header>
 {% endif %}
 {{ super() }}