docs: Add FAQ item about Windows

Add FAQ item about Windows.

doc/faq.rst

@@ -12,3 +12,14 @@ running ``asyncio.run(asyncio.sleep(1))`` in a notebook.) If you would like to l
 more about the problem, see the following issue: `ipython/ipykernel#548
 <https://github.com/ipython/ipykernel/issues/548>`_. This problem only affects Jupyter
 Notebook and derivatives. It does not affect IPython.
+
+Is Windows supported?
+---------------------
+
+If `WSL2 <https://docs.microsoft.com/en-us/windows/wsl/>`_ works for you, then
+the answer is "yes," otherwise the answer is "no."
+
+Experience has proven that supporting PyStan on Windows is challenging and
+requires a considerable investment of resources. If you would like to fund the
+development and ongoing maintenance of a version of PyStan which works on
+Windows, please post your proposal for discussion on the `Stan forum <https://discourse.mc-stan.org/>`_.