Adds link to RFC 9557

Author: zachleat

README.md

@@ -3,7 +3,7 @@
 Features:
 
 - Zero dependency super minimal ISO8601 date parsing library. Alternatives were [too lax, inaccurate, huge on disk, or huge in bundle](https://fediverse.zachleat.com/@zachleat/114870836413532617).
-- All dates supported by this library are RFC-9557 compatible (parseable by `Temporal.PlainDate.from`, `Temporal.Instant.from`, or `Temporal.PlainDateTime.from`) to prepare for wider [Temporal API](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Temporal) support.
+- All dates supported by this library are [RFC-9557](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Temporal/PlainDateTime#rfc_9557_format) compatible (parseable by `Temporal.PlainDate.from`, `Temporal.Instant.from`, or `Temporal.PlainDateTime.from`) to prepare for wider [Temporal API](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Temporal) support.
   - Note that this is not a full polyfill — not all RFC-9557 dates are supported here. Alternatives: [`temporal-polyfill`](https://github.com/fullcalendar/temporal-polyfill) or [`js-temporal/temporal-polyfill`](https://github.com/js-temporal/temporal-polyfill)
 - Invalid strings throw errors.
 - Time zone notes: