Make mistakes in machines more visible

[jackharding]

Description
As suggested by this comment, it would be nice if xstate warned you about silly mistakes. An example of such a mistake from that thread:

I was doing:

INCREASE_TIME: assign<Context, any>({ /* ... */ })

instead of:

INCREASE_TIME: {
    actions: assign<Context, any>({ /* ... */ })
}

Expected Result
Some kind of error alerting the user to the mistake.

Actual Result

Reproduction
#1833