toc shortcode: format html vs raw

[jamesbraza]

From https://geekdocs.de/shortcodes/toc/:

• What is the difference between format being html or raw?
• Should html or raw be put in quotes for standardization?

Happy to open a docs PR for this

[xoxys]

html adds a wrapper around it to support dynamic max level configuration and also adds a horizontal line after it while raw just adds the pure ToC provides by Hugo.