Add a WSL prerequisites section.

Author: Daniel-Khodabakhsh

src/doc/en/installation/source.rst

@@ -257,9 +257,11 @@ Some additional optional packages are taken care of by:
 
 .. literalinclude:: homebrew-optional.txt
 
+WSL prerequisites
+^^^^^^^^^^^^^^^^^
 
 Ubuntu on Windows Subsystem for Linux (WSL) prerequisite installation
-^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
 Sage can be installed onto Linux running on Windows Subsystem for Linux (WSL). These instructions describe a fresh install of Ubuntu 20.10, but other distributions or installation methods should work too, though have not been tested.
 
@@ -283,11 +285,17 @@ Sage can be installed onto Linux running on Windows Subsystem for Linux (WSL). T
 From this point on, follow the instructions in the :ref:`sec-installation-from-sources-linux-recommended-installation` section.
 It is strongly recommended to put the Sage source files in the Linux file system, for example, in the ``/home/username/sage`` directory, and not in the Windows file system (e.g. ``/mnt/c/...``).
 
+WSL permission denied error when building `packaging` package.
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
 You may encounter permission errors of the kind ``"[Errno 13] Permission denied: 'build/bdist.linux-x86_64/wheel/<package>.dist-info'"`` during ``make``.
 This usually comes from a permission conflict between the Windows and Linux file system.
 To fix it create a temporary build folder in the Linux file system using ``mkdir -p ~/tmp/sage`` and use it for building by ``eval SAGE_BUILD_DIR="~/tmp/sage" make``.
 Also see the `related Github issue <https://github.com/pypa/packaging-problems/issues/258>`_ for other workarounds.
 
+WSL post-installation notes
+~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
 When the installation is complete, you may be interested in :ref:`sec-launching-wsl-post-installation`.
 
 .. _section_cygwinprereqs: