gh-35843: Add a WSL prerequisites section
    
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### 📚 Description

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This PR adds a new section named **WSL prerequesites**, moving the WSL-
Ubuntu-specific section to as subsection and adding the WSL error under
it under its own subsection.
<!-- Why is this change required? What problem does it solve? -->
This change was made because originally the build error and solutions
appeared only under the WSL-Ubuntu-specific section but in reality this
impacts all flavours of WSL, not just Ubuntu.
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example "Fixes #12345". -->
Fixes #35840
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This is what the documentation looks like with this change:

![image](https://github.com/sagemath/sage/assets/9839187/0114b3c5-f7f5-
4bae-8ca0-de11581e1e5d)

which can be checked here: https://deploy-preview-35843--sagemath-
tobias.netlify.app/installation/source.html#wsl-prerequisites

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- [x] I have updated the documentation accordingly.

### ⌛ Dependencies

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None
    
URL: #35843
Reported by: Daniel-Khodabakhsh
Reviewer(s): Dima Pasechnik

Author: Release Manager

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: