Add examples of all the Markdown elements

It is necessary to have a page with an example of each Markdown elements, to show to the user how they are stylised by Buruma.

This example must be in the documentation site. Then, in the live site, should be a real example applying everything.

Start by locating the documentation site entry point and the corresponding live-site example area in the repository. Review how existing Markdown elements are documented and styled by Buruma. Done means the documentation includes an example of each Markdown element and the live site presents a real example applying them.

Written by the indexing model from the issue text.