isURL static method
Checks if string is URL.
Implementation
static bool isURL(String s) => hasMatch(s,
r"^((((H|h)(T|t)|(F|f))(T|t)(P|p)((S|s)?))\://)?(www.|[a-zA-Z0-9].)[a-zA-Z0-9\-\.]+\.[a-zA-Z]{2,7}(\:[0-9]{1,5})*(/($|[a-zA-Z0-9\.\,\;\?\'\\\+&%\$#\=~_\-]+))*$");