add bigint type to valid-typeof

[devsnek]

What is the purpose of this pull request? (put an "X" next to item)

[ ] Documentation update
[ ] Bug fix (template)
[ ] New rule (template)
[x] Changes an existing rule (template)
[ ] Add autofixing to a rule
[ ] Add a CLI option
[ ] Add something to the core
[ ] Other, please explain:

What rule do you want to change?
valid-typeof

Does this change cause the rule to produce more or fewer warnings?
fewer

How will the change be implemented? (New option, new default behavior, etc.)?
addition of type

Please provide some example code that this change will affect:

typeof 10n === 'bigint'

What does the rule currently do for this code?
fails

What will the rule do after it's changed?
doesn't fail

What changes did you make? (Give an overview)
added bigint as a valid type for valid-typeof rule, no tests added because most runtimes don't have this implemented yet.

Is there anything you'd like reviewers to focus on?

[jsf-clabot]

All committers have signed the CLA.

[ilyavolodin]

bigint is still a stage 3 proposal and ESLint usually doesn't support anything below stage 4. However in this case, it doesn't really hurt anything, so I'm not sure if it's just easier to add this change in. @eslint/eslint-team thoughts?

[devsnek]

v8 already has this implemented (save for a few methods) which is how i ran into this in the first place

[not-an-aardvark]

Also see #7417, which is a similar case.

I think I'm 👎 for doing this right now, because we don't accept explicit logic for features unless they're stage 4.

[devsnek]

i'll bump this when it hits stage 4 then 👍

[not-an-aardvark]

Closing because this isn't stage 4 yet, but feel free to create a new PR when it reaches stage 4.

[devsnek]

seeing as chrome 67 has bigint unflagged and node 10 LTS will land with v8 >= 6.7, even though its stage 3 can we not reopen this?

[not-an-aardvark]

Sorry, we generally don't support features until they reach stage 4. However, you could make a custom rule that works like valid-typeof but accepts comparisons to "bigint".