Added languages to code blocks for syntax highlighting

Added languages to code blocks for syntax highlighting + moved the comments in the YAML example so that they don't overflow the page (and add a scrollbar).

(we can't see it in the diff but the syntax highlighting makes the code examples much more readable)
Are you sure you had the backticks around the tag?

E.g. in the comment it displays like this: `</body>`

If I don't add the backticks: </body> (nothing is displayed but the tag is here)