[Ruby] Release 0.48.0

Fixed

• JSONSchema::Meta.valid? and JSONSchema::Meta.validate! incorrectly accepted some Draft 2019-09 schemas that the meta-schema rejects.
• Integers just outside the i64/u64 range incorrectly compared against numeric bounds through lossy f64 rounding (e.g. {"minimum" => -9223372036854775808} accepted -9223372036854775809).

Performance

• Faster multipleOf validation for integer instances with integer divisors, via integer arithmetic instead of floating-point modulo.