Add simple-acme to clients.json

[WouterTinus]

Important

• If this PR updates a file in content/en with a lastmod field, it must be updated.

• If this PR is a translation, please read TRANSLATION.md first.

[yuseok-kim-edushare]

to following Let's Encrypt's official guide for PR
we also need to update data/clients.json 's Line 2 "lastmod"

https://letsencrypt.org/docs/client-options/#adding-a-client-project

[WouterTinus]

Thanks, I've updated the date as well now.

[carehart]

Can anyone clarify why this pr is stalled? I'm not involved in it from either side: I'm simply a participant in the acme ecosystem, wanting to see that others learn (on the acme clients page) of simpleacme, as it's the key fork of winacme (by its primary maintainer).

Also, at what point might it make sense to remove winacme from the list, or at least to mark it deprecated/no longer supported. The front page if its repo makes that point clear. But folks following the link here to the winacme WEB SITE would not know it. The bottom of the simpleacme site offers a link to a page with the history of the two projects, for those uninformed: https://simple-acme.com/manual/about/simple-acme