Class syntax options in templates

Basic ships with no classes to work with. This approach was intentional so this implementation could be left to the desecration of the themer/frontend developer. However, I have found myself wanting a more developed starting point when I spin up a new project.

I have attached a patch that includes updates to node.twig.html and field.twig.html. Here I have outlined how devs can add "Classy inspired" or "BEM inspired" class names. This is commented out, so it would not change any markup until the code is enabled.

I thought I would share this here to see if others would find this useful. Look forward to your thoughts!

Cheers, Leah