Add unknown as simple type to array-type

[ThomasdenH]

PR checklist

• Addresses an existing issue: unknown support for 'array-type' #4085
• New feature, bugfix, or enhancement
  • Includes tests
• Documentation update: N/a

Overview of change:

Add unknown to the simple types. Updated tests to test this functionality.

CHANGELOG.md entry:

[bugfix] unknown is recognized as simple type in array-type

[palantirtech]

Thanks for your interest in palantir/tslint, @ThomasdenH! Before we can accept your pull request, you need to sign our contributor license agreement - just visit https://cla.palantir.com/ and follow the instructions. Once you sign, I'll automatically update this pull request.

[ThomasdenH]

I had marked this as WIP because I expected the unknown keyword to be undefined on older versions. But it seems to work in CI.

[JoshuaKGoldberg]

Awesome, thanks @ThomasdenH! Glad some kind of horrible hack around TypeScript versions wasn't necessary after all. 😄

What's probably happening: builds running with older versions of TypeScript would have type checking errors for an unknown name type in TS if we asked for them. TSLint still runs even if there are syntax or type errors so these are ignored. ts.SyntaxKind.UnknownKeyword will resolve to the right value if a new version of TS is resolved at runtime or undefined if an older version is.

[ThomasdenH]

I see. Well, it should make the other unknown issues simple to do as well!

[ThomasdenH]

Is it possible you missed this in the changelog?

[adidahiya]

ah, I actually missed it when cherry-picking commits onto the release branch. I'll get it in the next patch