Cancel promises on category search

[peterhil]

Cancel promises with something like AbortController for fetch.

Bluebird offers cancellable promises and there are other options.

For custom implementation the structure of Promise cancellation could be something like delayedExecution even though this handles callback execution.

• [ ] Cancel Promises for WebExtension API requests when user changes the search or clears the search

[peterhil]

Cancelable promise delay can be used instead of debounce and/or throttle to cancel when input changes: https://twitter.com/oliverjumpertz/status/1414510738119528449