Added option to mock error during fetch

[sadkebab]

Since fetch can throw errors on various conditions, I would expect this mock to give developers the ability to mock fetch error throws.

I implemented this feature by extending MockOptions with an optional throw property of type Error.
I also added a test to make sure that the mocked fetch call with throw an exception if the throw property is set.

[sadkebab]

There may be some type errors in the test file because the current tsconfig.json configuration throws an error importing "bun:test".

If executed the test will run successfully, but VSCode will show few type errors here and there.

[sadkebab]

Some suggestions to make contributing to this project easier from my experience making this PR:

Add default rules for a code formatter.

Consistency in coding style is very important in an open source project and having the rules defined as a configuration file for something like Prettier or Biome will make respecting the coding effortless for contributors

Fix the tsconfig.json

I was able to make the errors in the test file disappear by changing includes and excludes inside tsconfig.json but I didn't push those changes in the PR since the issue is unrelated to the content of this PR.

Add some simple contribution guidelines

The project structure is trivial but having a guideline on how to start contributing with a predictable setup process will make it easier for everybody.

I will be happy to open a new PR that will satisfy these concern if we discuss and agree on how to structure coding style rules beforehand.

[DRFR0ST]

Hey, thanks for the contribution! I'm super happy that you've brought up the contribution guidelines and default formatting rules. I have already started work on the two topics.

Sorry for the misconfigured tsconfig.json file. Would you mind creating a PR for the change that fixes the errors appearing in the test files?

[DRFR0ST]

LGTM 👌🏻

Thanks for the contribution! 🎉

[DRFR0ST]

@sadkebab would you like to contribute to the Biome set up PR?
#15