Thank you very much for this! Solved a few questions for me. :-)
* We can also determine whether or not the modal requires a selection
* before the button is enabled. It requires a selection by default,
* and since this is the experience desired, let's keep it that way.
Really had to laugh about that, because you don't say HOW you can set this option. I tried selectionRequired = false and required = false. Can't imagine any other variable names...
I wonder why there is no complete documentation of wp.media, it costs so much time to figure out how to set which option. :-(