Document AbortController removal and some improvements #1449
Description
What is the issue with the DOM Standard?
The Using AbortController and AbortSignal objects in APIs section lacks an example of how to remove the algorithm (and why, particularly as it relates to controlling browser UIs like a credential chooser). This came up in w3c-fedid/digital-credentials#463, where one needs to hold a reference to the algorithm to later remove it.
Also noting that WebAuth cites this section of the specification, then goes onto do things incorrectly (I think it never adds or removes the algorithm)... so we might need to clarify things a bit more about how to spec things properly.