* Add `spawn` as a way of calling promise-returning blocks
This change adds `spawn` which takes a no-argument, promise-returning
function, calls it, and returns `void`. This makes it easy to call
async blocks from `useEffect` and other places that don't take async
functions, but also makes such calls explicit.
* Adds interruptability to `spawn`
Now, the task function passed to `spawn` can take an `Interrupted`
argument, which is merely a method that returns `true` if the task
should stop doing work. Likewise, `spawn` returns an `Interrupt`
function that causes the `Interrupted` function to return `true`.
* Change to using `AbortController` and `AbortSignal`
Before, `spawn` used functions to interrupt and determine interruption
state. Now, based on feedback from @whscullin, it uses
`AbortController` and `AbortSignal`.
Tests now show how the controller can be used to abort long-running
tasks and API calls in the `spawn`. The also show how signals can be
chained using `addEventListener`.
* Fix `Apple2.tsx`
Forgot to change it to use `AbortController` and `AbortSignal`.
Co-authored-by: Will Scullin <scullin@scullin.com>
