Add missing bootstrap css to two examples

examples/cartodb.html

@@ -5,6 +5,8 @@ shortdesc: Example of a cartodb map.
 docs: >
   A simple example with an anonymous cartodb map
 tags: "simple, openstreetmap, attribution"
+resources:
+  - https://cdn.jsdelivr.net/npm/bootstrap@5.2.0/dist/css/bootstrap.min.css
 ---
 <div id="map" class="map"></div>
 <form class="row">

examples/cluster.html

@@ -5,6 +5,8 @@ shortdesc: Example of using ol/source/Cluster.
 docs: >
   This example shows how to do clustering on point features.
 tags: "cluster, vector"
+resources:
+  - https://cdn.jsdelivr.net/npm/bootstrap@5.2.0/dist/css/bootstrap.min.css
 ---
 <div id="map" class="map"></div>
 <form>