Add loadEventCallback

[jasonabrown]

The JS SDK allows for a callback on certain methods. Since the React SDK handles _ps("load") under the hood we need allow users to specify an error handling callback for this method.

Verified locally.

[cdhcs1516]

Can you check the indents? They look abnormal.

[cdhcs1516]

@jasonabrown and do we want to add this prop to the documentation?

[jasonabrown]

@cdhcs1516 thank you for the quick review! Curious your thoughts on naming convention for this prop. We could alternatively call it onLoad, but clarify in the documentation that it is not included in onAll.

[cdhcs1516]

@cdhcs1516 thank you for the quick review! Curious your thoughts on naming convention for this prop. We could alternatively call it onLoad, but clarify in the documentation that it is not included in onAll.

onLoad sounds good. But why is it not included in onAll? This function always gets called during _ps('load'), right?

[jasonabrown]

@cdhcs1516 the underlying JS SDK does not have a trigger event for load so we instead rely on the event_callback argument.

[brdly-smith]

LGTM, do we still need this @jasonabrown ?