Force format to absolute iso8601

This code runs on github.com and displays timestamps in relative formatting...
but I really NEVER want to see timestamps in relative form.

I'd so much rather that 'last week' show up as '2024-09-26 19:05:24' or anything similar to iso8601.

Perhaps this just needs a new format string (for non-duration timestamps) of 'iso8601' ?

I can convince github pages to reveal an absolute timestamp with the following snippet pasted into the console.
```
document.querySelectorAll('relative-time[datetime]')
.forEach( item => {
item.setAttribute('format','datetime')
item.setAttribute('formatStyle','long')
item.setAttribute('precision','minute')
});
```
... but I get 'Thu, Sep 26' which is way too short.

I can use this snippet to update the title to show what I want but I still have to hover
```
document.querySelectorAll('relative-time[datetime]')
.forEach( item =>
item.setAttribute(
"title",
new Date(
Math.round(
Date.parse( item.getAttribute("datetime") )
/ 60000 ) * 60000
)
.toISOString()
.replace(/T/," ")
.replace(/[.].*/,"")
+" UTC"
)
)
```

perhaps I should be looking to convince Intl.DateTimeFormat with a Locale that emits iso8601 instead?

まず、issue で言及されている相対時間フォーマットのオプションと Intl.DateTimeFormat の動作を確認します。ユーザーが相対テキストの代わりに ISO 8601 形式の絶対タイムスタンプを要求でき、出力が現在の 'Thu, Sep 26' 形式より大幅に長くなれば完了です。

索引モデルが issue の本文から書いたものです。