Fix ESLint errors and JSDoc comments in linters

[queengooborg]

This PR fixes up the issues reported by ESLint, as well as updates the JSDoc comments, and performs just a little bit of refactoring for efficiency and consistency in the linter files.

[ExE-Boss]

You shouldn’t be using ESLint to validate JSDoc types, as its parser is woefully out of date.

I recommend using TypeScript’s JSDoc validation instead, as it ensures that the declared types match what’s being used.

[queengooborg]

FYI @ExE-Boss, I am not using ESLint's built-in JSDoc checks to validate the JSDocs. Instead, I am using a dedicated plugin that is actively maintained (its last release was 13 days ago).

[ExE-Boss]

I forgot that I wanted to mention this last time:

[ddbeck]

This PR appears to partly relate to #5252 and #5635 (comment).

I'm going to suggest closing this PR and breaking it into pieces. It looks like there's a grab bag of changes here: copyright notices (which I'm opposed to generally—I've opened #5879 on this topic), hashbang lines, and JSDoc comments. The ESLint connection seems to be an ESLint plugin that checks for… something that I don't think has been described anywhere. I'd like to be able to review and discuss these separately, since they don't seem to be dependent on each other.

[queengooborg]

Sounds good to me, I'll start breaking this down then! I'll mark this as "not ready" and leave it open until the separate PRs have been created.