* Create timestamp.js
Taken verbatim from @ericshulman.
* Add description of the timestamp suffix
* Add an example for timestamp use
I also snuck it a couple of cosmetic corrections, because I was too lazy to open a new PR. 😢
* Correct example 4 to use the right date formats
* Correct description of the default date format
* Add a test for the timestamp suffix
* Add more format:timestamp tests
* Drop invalid input
* Update version tag in docs
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Co-authored-by: jeremy@jermolene.com <jeremy@jermolene.com>