Update documentation for librabbitmq dependencies

[dolsysmith]

We've found that librabbitmq doesn't work with versions of Python 3.8 other than 3.8.12. In order to get it working for development, I had to do the following.

1. Build Python 3.8.12 from source. This documentation was helpful.
2. Install additional dependencies, per this issue on the Celery repo:

sudo apt-get install libpython3.8-dev
sudo apt-get install -y --no-install-recommends \
        autoconf \
        automake \
        pkg-config \
        libtool

We should add this to the docs under the Development section.