Demo flipswitch with custom label

[gabrielschulhof]

Originally from #6652 (comment)

[gabrielschulhof]

I'll also update the API docs with the CSS necessary for label placement and, if I can, for switch size.

[gabrielschulhof]

@patrioticcow AFAIK flip switches do not autosize to accommodate the label. You must specify the size using custom CSS. This will be documented in the API docs.