JavaScript guides

This first batch publishes 2 of the 5 upstream JavaScript guides; the rest are converted and will be released in later batches.

• Coordinating Global Events with Temporal — Schedule future meetings or events by explicitly binding them to a geographical IANA time zone so that event times remain accurate regardless of Daylight Saving Time (DST) transitions, “skipped” or “repeated” hours during clock changes.
• Supporting Global Calendar Systems with Temporal — Display and calculate dates in non-Gregorian calendar systems (e.g., Islamic, Hebrew, or Chinese) accurately for international users.