Checks if value
is of type Array and returns true
if so, or false
if not.
let result1 = gmynd.isArray( 270 ); // will return false
let result2 = gmynd.isArray( "Hello!" ); // will return false
let result3 = gmynd.isArray( ["a", "b"] ); // will return true
let result4 = gmynd.isArray( {x:123, y:456} ); // will return false