Markup for: block module

Liam Morland → made their first commit to this issue’s fork.

I have made an issue fork and merge request that updates block.html.twig:

• Allow the wrapper element to be customized
• Default to wrapping blocks with labels in section
• Allow customizing the label element

postponing on the decision over at 🐛 Do not use `article` elements without a header Needs work since they seem to be related.