Include some of the docstring information in the output webpage

In many recipes, such at [the CAPE ratio](https://metoffice.github.io/CSET/reference/operators.html#CSET.operators.convection.cape_ratio) there is a substantial amount of useful scientific information in the Notes section of the docstring. This is not exposed in the output webpage currently, where it would be really useful.

Start with the generated CAPE ratio reference page linked in the issue and compare its output with the recipe docstring's Notes section. Trace how docstrings become the output webpage, then expose the relevant Notes content and verify that the rendered page includes it.

Written by the indexing model from the issue text.