Option to add Copy To Clipboard button for Text & TextArea

[KT Walrus]

I need to add a "Copy to Clipboard" button to a couple of Text and TextArea form fields. 

Please add an option to do this to the Text & TextArea form helpers. Without this button, it is very hard for my users to select text and copy it to the clipboard on mobile.

See the Javascript Selection and execCommand APIs that seem to be well supported by most browsers these days.