Prefer singular unit names in documentation

[justingrant]

Fixes #1486 to prefer singular names of units in smallestUnit/largestUnit/unit option values.

Includes a few other minor changes (mostly whitespace) due to running prettier on docs code samples.

[codecov]

Codecov Report

Merging #1492 (108b14d) into main (d9a1cdb) will not change coverage.
The diff coverage is n/a.

❗ Current head 108b14d differs from pull request most recent head c6755f3. Consider uploading reports for the commit c6755f3 to get more accurate results

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  Coverage   95.58%   95.58%           
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  Files          19       19           
  Lines       11139    11139           
  Branches     1736     1736           
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  Misses        486      486           
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test262	61.02% <ø> (ø)
tests	91.76% <ø> (ø)

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[ptomato]

I'd recommend not mentioning the plural units at all in the documentation. I think that would draw more attention to them than needed.

Will mark this as draft so it's not accidentally merged until we can get consensus on the normative change, but otherwise this seems fine.

[ptomato]

The main change achieved consensus at today's TC39 meeting.