Update current docs to follow the Diataxis approach

[R-Lawton]

WHAT

Review the current docs to categorise them into 1 of the 4 Diataxis types. This may not be clear in all cases and may require deeper investigation than an initial review, in particular if a document fits into more than 1 type.

For example, hand holding like a tutorial mixed into a guide (here are some examples of this).

Outcomes of this will be:
Site nav changes for docs that are not in the most appropriate place. For example, put all guides in ‘How-to Guides’ and reference material in ‘Concepts and APIs’.
Updates to docs that don’t fit a singular purpose. This could mean splitting the doc into 2 or more docs, or rewriting it to have a single focus.