docs: rSTify the "SubmitAPatch" wiki

docs: rSTify the "SubmitAPatch" wiki

- The original wiki is here[1]. I copied the wiki source[2] into a .wiki
  file, and used `pandoc` to convert it to rST:

    $> pandoc -f Mediawiki -t rst submitting-a-patch.wiki -o
       submitting-a-patch.rst

- The only minor touch-ups I did was to fix URLs.  But 99%, it is a 1-1
  conversion.

  (An example of a "touch-up": under the section "Patch emails must
  include a Signed-off-by: line", I updated the "see SubmittingPatches
  1.12"  to "1.12) Sign your work")

- I have also converted a couple other related wiki pages (included in
  this patch series) that were hyperlinked within the SubmitAPatch page,
  or a page that it refers to:

  - SubmitAPullRequest: https://wiki.qemu.org/Contribute/SubmitAPullRequest
  - TrivialPatches: https://wiki.qemu.org/Contribute/TrivialPatches

- Over time, many people contributed to this wiki page; you can find all
  the authors in the wiki history[3].

[1] https://wiki.qemu.org/Contribute/SubmitAPatch
[2] http://wiki.qemu.org/index.php?title=Contribute/SubmitAPatch&action=edit
[3] http://wiki.qemu.org/index.php?title=Contribute/SubmitAPatch&action=history

Signed-off-by: Kashyap Chamarthy <kchamart@redhat.com>
Message-Id: <20211110144902.388183-4-kchamart@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
[thuth: Cosmetic fixes]
Signed-off-by: Thomas Huth <thuth@redhat.com>