Issue 1933 - Cancellation of requests when no longer needed

[CaptainPants]

First attempt at #1933 - adding a cancellation mechanism to fetchers.

Looking for feedback on the approach and if there is any huge landmines I'm missing. I won't be offended if this is just a big 'no'.

Still working on how to appropriately test this.

TODO:

• Not sure how error handling works as this will cause the await to throw a DOMException from the abort call, and don't want this to send the hook into an error state.
• Testing.
• Tests - fix existing ones and add new ones related to the change.
• Add an example?

[codesandbox-ci]

This pull request is automatically built and testable in CodeSandbox.

To see build info of the built libraries, click here or the icon next to each commit SHA.

Latest deployment of this branch, based on commit aa869c7:

Sandbox	Source
SWR-Basic	Configuration
SWR-States	Configuration
SWR-Infinite	Configuration
SWR-SSR	Configuration

[700software]

I would like for this feature to be enabled by default. Not the other way around.

Let's emphasize what the new users want rather than reverse compatibility since the risk of problems is low.

Would a new user who has no prior version of swr installed prefer this on by default or not? I think yes but I'm only one user.

[davidnormo]

Agreed

[davidnormo]

Is there anything missing from this preventing it from being merged?

[oanaOM]

This would be very helpful to have! Any ideas when will this get released?
Meanwhile, is there other workaround to make SWR work with AbortController or achieve a cancelling mechanism?

[scarqin]

Exciting features! looking forward to launch.