chore: make followRedirect option accept functions

[VanTigranyan]

Checklist

• I have read the documentation.
• I have included a pull request description of my changes.
• I have included some tests.
• If it's a new feature, I have included documentation updates in both the README and the types.

[VanTigranyan]

With these changes, it is possible to pass the followRedirect option as a function that gets a PlainResponse right before the redirect is done and returns true or false. By that, it is possible to decide whether to redirect dynamically. The option supports both plain boolean and function type, allowing users to decide for themselves which type they prefer.

[VanTigranyan]

@sindresorhus Made the fixes you asked for. Thanks for the quick review.

[VanTigranyan]

@sindresorhus BTW: I would be happy to contribute by adding a semantic release setup that would increase the version of the lib based on commit messages and would publish automatically.

[sindresorhus]

I would be happy to contribute by adding a semantic release setup that would increase the version of the lib based on commit messages and would publish automatically.

No thanks. I prefer the human touch to releasing and changelogs.