add support for signal request option

[nicknisi]

Type: feature

The following has been addressed in the PR:

• [x] There is a related issue
• [x] All code has been formatted with prettier as per the readme code style guidelines
• [x] Unit or Functional tests are included in the PR

Description:

Note: This PR is dependent on dojo/shim#143.

Resolves #390

add support for a signal: AbortSignal property in the request options. When provided, the request can be aborted by calling the AbortController#abort method, similar to the fetch API. When a request is aborted, the Promise is rejected with an AbortError, if possible.