Multiple toctrees with captions

[tristanlins]

I write a "big" documentation that covers multiple components.
In the main index.rst multiple toctrees are used like this:

.. toctree::
   :name: toc_index
   :maxdepth: 1

   root/page1
   root/page2
   root/page3

.. toctree::
   :caption: Component A
   :name: toc_component_a
   :maxdepth: 1

   compA/page1
   compA/page2
   compA/page3

.. toctree::
   :caption: Component B
   :name: toc_component_b
   :maxdepth: 1

   compB/page1
   compB/page2
   compB/page3

The captions in navigation are not styled properly.
I've added a custom css for these captions:

div.sphinxsidebar .sidebar-toc .caption {
    margin: 17px 0 0 0;
    padding: 0 22px 6px;
    font-size: 14px;
    font-weight: bold;
    color: #606060;
}