Fixed a bug where (find:) would incorrectly error when the lambda used the it identifier, and the second value given to it was "", 0, or false.

Also:

 * Eliminated CustomCommand.create() and made the constructor public again.
 * (lch:) colours are no longer converted to RGBA when used, instead using the modern CSS lch() function.
 * Increased the maximum acceptable C value given to (lch:) from 132 to 150.
 * Now, using the spread syntax on invalid values (like numbers) will produce a more instructive error message in more cases.
 * Improved the error message for the case where (sorted:)'s lambda didn't produce a string or number.