feat: fetch proxy

[ojeytonwilliams]

Checklist:

• I have read freeCodeCamp's contribution guidelines.
• My pull request has a descriptive title (not a vague title like Update index.md)

It's a bare-bones implementation, but it should support the functions we currently use and let devs know when they try to use something that's yet to be implemented

[ShaunSHamilton]

Is this just useful for spying on the stuff?

[ojeytonwilliams]

Mostly it's so we can fix this: freeCodeCamp/freeCodeCamp#60874

[ShaunSHamilton]

Last question: Do we want to default to replacing fetch? Or, instead just offer a fetchProxy?

[ojeytonwilliams]

That's a good question... and one I should have thought about.

I'm leaning towards replacing fetch by default just because it's less work on both sides. Partly because it's straightforward, partly because I can't think of a reason not to (other than the unimplemented functionality), but mostly because it's reversible. Nothing gets locked in if we choose the path of least resistance.

What do you reckon?

[ShaunSHamilton]

Good point. If it works, worst case scenario is eventually creating a challenge (test) that needs a change.

[ShaunSHamilton]

Pending merge conflict 👍