Add tests related to error handling.

Traditional British long count is available for systems.

Only largest millia should remove prefix when group is 001.

Make word positive when making negative a negative number.

Make short millia parse and stringify correctly.

Use special millions prefix only when millia is less than one.

Add namespace for short/long count. Also manage conversion configs and defaults.

There is only a certain string length allowed to convert parsed numbers to bigint.

Ensure strings are properly sanitized before processing.

Ensure exponents are normalized properly.

Use bigint for place values to be more adaptable with longer inputs.

Put functions with different purposes into their own files.