Add MANIFEST.in into tutorial

[Kani999]

In the tutorial is missing creating a MANIFEST.in file.
When missing without proper lines

recursive-include <plugin_folder>/templates *

it causes the django.template.exceptions.TemplateDoesNotExist: <plugin_name>/<templates>.html when installing within a netbox.

[Lay3r8]

I had the same issue and it was indeed resolved thanks to @Kani999 's advice by adding a MANIFEST.in file near setup.py with the following content:

recursive-include netbox_access_lists/templates *