Support extended ISO 8601 Duration format

[robross0606]

The ISO8601 extended Duration specification supports things like negative durations and the upcoming Temporal API appears to support that. Is Pomeranian Durations planning on supporting negative durations once the Temporal API is fully available?

[robross0606]

I just realized that P-1Y is supported but not -P1Y. From what I understand, both should be possible under the specification.