Use iso8601 datetime format in docs site

[scarf005]

Is your feature request related to a problem? Please describe.

1. the metals docs site use multiple time formats, which is inconsistent.

DD MM YYYY	MM DD YYYY	YYYY-MM-DD

2. due to date formatter using local datetime format, locally served sites will render differently formatted time string. this can be workaround via setting timezone but still is inconvenient.

https://github.com/scalameta/metals/blob/3f04322dcc572ca167a6e428eab633542cbe7a3b/metals-docs/src/main/scala/docs/Snapshot.scala#L19-L24

(this is malformed, the 'human-readable' datetime format in korea would be 2024년 8월 23일 00:15)

Describe the solution you'd like

Change date formatter to use iso8601 (YYYY-MM-DD) or RFC 3339 (for 'human readable' ) time format, as it's unambiguous, easy to sort and recognized worldwide. it's already used on releases.

I'm willing to open a PR. Check scalameta/metals@main...scarf005:metals:docs/use-iso8601 for proposed solution.

Describe alternatives you've considered

keeping the date format as-is.

Additional context

most asian countries use YMD datetime format by default.

Search terms

date, time, datetime, human-readable format, iso8601