URL support for the sync feature of tab sets

[kaycebasques]

We have a single setup page for macOS, Windows, and Linux. Assume the URL is https://pigweed.dev/setup.html. We're using tabs and the tab sync feature to organize the content by OS.

---------------------
Install prerequisites
---------------------

.. tab-set::

   .. tab-item:: Linux
      :sync: linux

      ...

   .. tab-item:: macOS
      :sync: macos

      ...

   .. tab-item:: Windows
      :sync: windows

      ...

------------------
Configure settings
------------------

.. tab-set::

   .. tab-item:: Linux
      :sync: linux

      ...

   .. tab-item:: macOS
      :sync: macos

      ...

   .. tab-item:: Windows
      :sync: windows

      ...

By default the Linux tabs is shown. We want to be able to provide URLs that load with the Windows tabs shown.

It seems that Furo uses data-sync-id HTML attributes to coordinate syncing. We would be OK with something like this: https://pigweed.dev/setup.html?sync=windows

[pradyunsg]

This isn't really a Furo-specific request, but rather for the extension.

pradyunsg/sphinx-inline-tabs#27