added a more robust (but succinct) e.g. of showing/hiding tooltip in readme

[matthewliuswims]

The previous e.g. for showing/hiding tooltip manually was good, but I thought could be improved, as for e.g. I was not sure what {open} was in open={open}

Also, I only realized setIsOpen() in previous e.g. worked because we were assuming a controlled component.

So my pr does the following:

1. explicitly show that when using the prop open, we probably need a controlled component with

state = {
  open: false,
}

2. demonstrate the ability to have a tooltip with a click trigger, which can then linger for a set amount of time (making this e.g. more practical and robust)
   setTimeout(() => alert('can do things after delay'), 2000);