Clarification to paramter el

[ppazos]

Current README has:

el (optional, string, Element) - this parameter is optional but if no selector or element is passed it defaults to body.

This doesn't specify that the el selector or element is the container of the DOM generated by the picker.

For instance, I have specified the selector as a class of an input field and that doesn't work, it should be a container element like a div, which is not clear in the current spec.

[priyank-p]

Can you do a please quick PR clarifying that if possible? I won't be able to get to it until next weekend.