This extracts all of the attributes from a `CloudEventVX` that
are not generated by the constructor (id and specversion) into their
own `CloudEventVXAttributes` interface which the `CloudEventVX`
interface extends. This allows TS devs to optionally provide `id`
and `specversion` with proper autocompletion.
Additionally, I have added a union type, `CE` in `cloudevent.ts` which
represents any of `CloudEventV1`, `CloudEventv03`, `CloudEventV1Attributes`
and `CloudEventV03Attributes` interfaces.
Finally, this commit changes all of the user facing API to be `.ts` instead
of `.js` files.
The existing documentation in `./docs` was removed. It should be replaced with generated
HTML from tsdocs, pending some other method of publishing API documentation. That will
come as a separate, docs-only PR.
Fixes: https://github.com/cloudevents/skd-javascript/issues/188
Signed-off-by: Lance Ball <lball@redhat.com>