Replace sphinx-rtd-theme with Furo

[kevinbowen777]

Install Furo Sphinx theme

Documentation:

• Furo Documentation Repository:
• Furo Source Code Modify docs/conf.py as follows:

"""Sphinx configuration."""
project = "bookstore"
author = "Kevin Bowen"
copyright = f"2023, {author}"
#
html_theme = 'furo'
html_logo = 'django_24.png'
html_title = 'bookstore'
extensions = [
    'sphinx.ext.duration',
]