isolated modules and almost isolated declarations

[wjhsf]

isolatedModules and isolatedDeclarations provide guardrails that help make type checking faster / more portable. We don't actually need the flags enabled for our current build process / target, but it makes the code more portable if we decide to make changes in the future. And the code changes are pretty trivial, so I figured why not.

Note that we can't actually enable the isolatedDeclarations flag because we use a symbol as a property key, but I've made all the other changes to be 99% compatible.

tough-cookie/lib/cookie/cookie.ts

Line 548 in 8e39ae1

[Symbol.for('nodejs.util.inspect.custom')](): string {