More clearly indicate the requirements for calculating indicators and indices

[Zeitsperre]

Problem

The primary method for determining what variables are needed to calculate a given index or indicator is to look at the call signature (sometimes very busy) and/or the Parameters entries. This can be annoying for users as they might want to calculate something and gloss over a variable that might be required.

Potential Solution

Each index or indicator could list before the Parameters section a block that lists these requirements. e.g.:

Requires
--------
# <standard_name> (variable)
temperature (tas), precipitation_flux (pr), geopotential (z)

[aulemahal]

I don't get the "and indices" part of the issue ? Indices are documented through normal function docstrings, which explicitly lists the parameters ?

For indicators, we could simply add the required and optional variables to the short version of the indicator doc in the "Climate Indicators" page.

[Zeitsperre]

@SarahG-579462

Feel free to edit this issue and/or elaborate on how you'd like to see things change.

[huard]

I think we should stick with the numpy doc convention. https://numpydoc.readthedocs.io/en/latest/format.html

Question: does this relate to the HTML docs or the help you get within a Python shell ? If it's the HTML, we could possibly tweak the CSS to highlight some parameters.

[Zeitsperre]

Fixed with #1454