test.concurrent support

it appears that the linter ignores test.concurrent calls, for example - currently I have the jest/no-empty-title rule enabled:

with just test:

[G-Rath]

@daniellacosse from memory, a couple of things need doing:

• concurrent needs to be added as a value in the right enum,
• concurrent should be checked for what it supports, as while I suspect it is only test.concurrent, we need to know if it.concurrent, test.concurrent.only, test.concurrent.each, etc are valid in jest.
• All the rules should be checked, as jest/no-empty-title isn’t the only one that this affects (or maybe it is - either way, need to check).
• The jest/no-empty-title rule needs to be updated to include concurrent in what it checks. iirc this could be just a matter of adding it to the right enum, but otherwise it’ll just be a matter of passing the new enum value in the right place.

[SimenB]

Go for it!