Disabling `exhale` because it is just overloading things right now.

Hidden in this commit are a couple of other items:
* Enable .md documents for CONTRIBUTING.md to avoid same content not on
  docs.beagleboard.org
* Added graphviz to the venv setup, but that doesn't do much as I think
  it was already there

commit c761ac17
Author: Deepak Khatri <lorforlinux@beagleboard.org>
Date:   Mon Nov 14 01:19:14 2022 +0530

    Table rotation and font size change

commit 216bdb44
Author: Deepak Khatri <lorforlinux@beagleboard.org>
Date:   Mon Nov 14 01:18:26 2022 +0530

    Fix ref link

commit 4ebaf63b
Author: Deepak Khatri <lorforlinux@beagleboard.org>
Date:   Sun Nov 13 23:51:45 2022 +0530

    Update BeagleBone Black headerpin table font size

commit 168c12e9
Author: Deepak Khatri <lorforlinux@beagleboard.org>
Date:   Sun Nov 13 23:39:01 2022 +0530

    Add GNU FreeFont

commit 5389ee61
Author: Deepak Khatri <lorforlinux@beagleboard.org>
Date:   Sun Nov 13 23:32:42 2022 +0530

    Fix font package name

commit 751f9df9
Author: Deepak Khatri <lorforlinux@beagleboard.org>
Date:   Sun Nov 13 23:3...

commit 4ab3ff82
Author: Jason Kridner <jkridner@beagleboard.org>
Date:   Tue Oct 25 21:38:16 2022 -0400

    More spelling fixes

commit fce576ba
Author: Jason Kridner <jkridner@beagleboard.org>
Date:   Tue Oct 25 13:52:28 2022 -0400

    Fixed a bunch of spelling and linking errors

commit 185218ee
Merge: 39c2dd78 c3b7fb7f
Author: Jason Kridner <jkridner@beagleboard.org>
Date:   Mon Oct 24 13:58:46 2022 -0400

    Merge branch 'main' of git.beagleboard.org:docs/docs.beagleboard.io

commit 39c2dd78
Author: Jason Kridner <jkridner@beagleboard.org>
Date:   Mon Oct 24 13:54:54 2022 -0400

    books/pru-cookbook/code: fix some spelling issues

commit c3de7ef6
Author: Jason Kridner <jkridner@beagleboard.org>
Date:   Mon Oct 24 13:44:15 2022 -0400

    books/pru-cookbook: fix references to code

commit c4a51c22
Author: Jason Kridner <jkridner@beagleboard.org>
Date:   Mon Oct 24 12:18:03 2022 -0400

    books/pru-cookbook: move code to submodule

* List all boards in top-level ToC
* Fix BeagleConnect headings and general clean-up