Add react/no-array-index-key rule example to documentation

[dmmarmol]

Improve documentation of this particular rule by adding a use case example.

[ljharb]

generally we don't document things like this, because it's basics of how eslint itself works. It's assumed that users of an eslint plugin know how eslint works.

[dmmarmol]

I see your point but, as an eslint user, sometimes I found that there're many rules that either exptects a string like error or warn, while others could expect numbers, booleans or even objects or arrays. This made me waste some time until I found some example in the web about the correct usage of a specific rule.

I personally think that documenting this doesn't distract the user and also helps on document how this specific rule works.

[ljharb]

If so, then let's also audit every other rule doc, and make sure they all document themselves the same way?

[ljharb]

(do note tho, every rule without exception supports 0/1/2 or "off"/"warn"/"error"; the variability is only in additional configuration arguments)

[dmmarmol]

I'd love to see every rule documented, but as you know there're a lot of them and it's better to start at some point if you truly consider it.
On the other side (and since I don't consider myself a an advanced eslint user), I wasn't fully aware of that rule (my bad for don't reading the eslint docs ✋).
As a conclusion, I see that you have a valid point about being redudant adding this as a documentation, but maybe it could help some begginers or anxiety devs like me :).

[ljharb]

I definitely think reducing confusion is good; but i don't think doing it piecemeal is likely to be effective.