changed the colour of edit buttons

web/app/templates/examples.html

                 <span class="badge bg-secondary">{{ example['created'].strftime("%Y-%m-%d %H:%M") }} UTC</span>
                 {% if current_user.is_authenticated %}
                 <a href="{{ url_for('example.edit_example', example_id=example['id']) }}">
-                    <span class="badge bg-warning">Edit</span>
+                    <span class="badge bg-dark">Edit</span>
                 </a>
                 {% endif %}
             </div>

web/app/templates/practices.html

                 <span class="badge bg-secondary">{{ practice['created'].strftime("%Y-%m-%d %H:%M") }} UTC</span>
                 {% if current_user.is_authenticated %}
                 <a href="{{ url_for('practice.edit_practice', practice_id=practice['id']) }}">
-                    <span class="badge bg-warning">Edit</span>
+                    <span class="badge bg-dark">Edit</span>
                 </a>
                 {% endif %}
             </div>

web/app/templates/tool.html

     {% if current_user.is_authenticated %}
     <div class="row text-center py-3">
         <a href="{{ url_for('tool.edit_tool', tool_id=tool['id']) }}">
-            <span class="badge bg-warning">Edit</span>
+            <span class="badge bg-dark">Edit</span>
         </a>
     </div>
     {% endif %}