no-shadowed-variable should ignore shadowed _-params

[ozra]

Having a few nested arrow functions that throw away the argument shouldn't be considered shadowing. Bad taste perhaps. But not shadowing.

[lukyth]

What about a case when _ was used for lodash; i.e. import _ from 'lodash'? _ in function argument would probably be considered as shadowed in that case.

An option to allow some variable name to be shadowed like what ESLint does with its no-shadow rule might be better. Then shadowed _ can be allowed if lodash is not being used.

[tao-cumplido]

Just came across this myself when I noticed that typescripts lets me use _ as argument name with compiler flag noUnusedParameters enabled.

I then stumbled upon this issue which states that any name starting with _ is allowed and suggests using names like _1, _2, etc. for multiple unused parameters. The same approach can be used to prevent the linting rule from triggering.

[JoshuaKGoldberg]

Seems reasonable to add an opt-in option for the rule to enable this kind of shadowing.