[docs] Create documentation for documentation (getting started template, useful tips/tricks)

[andrewnicols]

What is the Moodle feature that needs documenting?

For documentation we should document some tips and tricks on getting started, for example:

• a getting started template
• useful markdown frontmatter
• links to the frontmatter docs
• useful components (Since, ValidExample, InvalidExample)
• other useful things (including examples from file, etc.)

Is this documentation specific to a Moodle version?

No

Are you able to provide a patch for this?

Yes - I will create one