Updated README.md
Updated README.md

Added direct link to https://www.npmjs.com/package/intl-tel-input
for the NPM hyperlink (saves people searching on NPM themselves and possibly selecting the wrong package)
Bluefieldscom/intl-tel-input,jackocnr/intl-tel-input,jackocnr/intl-tel-input,Bluefieldscom/intl-tel-input