docs/builder: touch up markdown, and some minor rephrasing
docs/builder: touch up markdown, and some minor rephrasing

- add code-fences with code-hints so that the right hightlighting is applied
- replace `*` for `-` in bullet-lists for consistency with other parts of the
  documentation.
- reduced number of "notes", either by combining some, or by changing some
  to regular text.
- removed "line numbers" from some examples, because there's only four lines,
  which should not need really need line numbers.
- reformat some notes to our new format

Signed-off-by: Sebastiaan van Stijn <64b2b6d12bfe4baae7dad3d018f8cbf6b0e7a044@gone.nl>

thaJeztah/cli,docker/cli,cpuguy83/cli,cpuguy83/cli,thaJeztah/cli,docker/cli