[DOCS] Need comprehensive list of function modifiers

[ChrisChinchilla]

Abstract

The docs need a list on one place of all function modifiers, and a summary of what they do, or link to more details.

Motivation

In PR #5796 we discussed linking to function modifiers section, which doesn't summarise what's possible.

[chriseth]

Note that "function modifier" in the strict sense is just what users can define using modifier, although we sometimes also use the name function modifier for things like private and external. Perhaps we should call the built-in ones "qualifiers"?

[NunoFilipeSantos]

Hi! 👋 This issue is stale, and for that reason we're closing it for now.