I've introduced the type="date" attributes support (eg: min, max) and added format to the input attributes. This way, it can almost be a full polyfill, it'll still replace the type attribute with `text` so that the browser doesn't interfere with handled events/value.
Thank you, I appreciate the effort and the documentation. If you want to propose a full-polyfill behaviour, you could make a new module for that. Then you won't have to worry about the code size when adding the missing parts of the standard like valueAsDate: https://gist.github.com/sylvainpolletvillard/0aa9df9c180cd007e5e1