Use today for today, and omit current year

[khiga8]

Based on feedback, this PR updates the format when users prefer absolute time, to provide more contextual information for recent dates:

• Replace the date with localized "Today" when the timestamp is today
• Omit the current year from dates

This was a decision based upon user feedback.

Approach

The desired format Today, 2:34 PM EDT isn't natively supported by Intl.DateTimeFormat, so this PR combines:

1. Localized "Today" string (via RelativeTimeFormat)
2. Localized time format (via DateTimeFormat)

Assumptions & trade-offs

This approach assumes:

• The order "Today" then the time, is universally reasonable across locales.
• Combining localized "Today" and localized time produces acceptable formatting across locales.
• Space is an acceptable separator across locales.

Alternative considered

Hard-coding this custom format for English-only, but feels unideal/inconsistent to special-case a format for english-only.

Examples

English:

Today, 2:34 PM EDT          (en-US, today)
Dec 24, 2:34 PM EDT         (en-US, this year)
Dec 24, 2024, 2:34 PM EDT   (en-US, past year)

TBD

• Is space an acceptable separator between "Today" and time across locales?