CloudEvent data in Array format throws a ValidationError

[lance]

Describe the Bug

When creating or receiving a CloudEvent, if the data is in the form of an Array - which is valid JSON - we get a validation error.

Steps to Reproduce

1. use new CloudEvent() to create an event with the data property as an array. For example:

const ce = new CloudEvent({ source: '/test', type: 'example', data: [ 1, 2, 3 ] });

That will produce:

   TypeError: invalid payload
      at Object.validateV1 (src/event/spec.ts:14:11)
      at CloudEvent.validate (src/event/cloudevent.ts:178:16)
      at new CloudEvent (src/event/cloudevent.ts:121:10)

Expected Behavior

No error thrown.

Additional context

The schema seems to have wrongly typed data here https://github.com/cloudevents/sdk-javascript/blob/master/src/event/schemas.ts#L12-L14 and here https://github.com/cloudevents/sdk-javascript/blob/master/src/event/schemas.ts#L91-L93

[lance]

Although the schema has not changed, in previous versions the event was (in most cases) validated on demand. With the new version, you are not allowed to create an invalid event. In this case, the event is not invalid, but the schema thinks it is.

[lance]

The fix for this also adds tests for boolean and null which are also valid JSON.