[docs] Fix typos

[jimt]

Description

Copy editing of the Caddy reverse proxy doc

Checklist

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[tsmethurst]

Hiya, could you possibly open another version of this PR (or amend this PR) to only include actual typos? There's opinionated grammar stuff in there that really doesn't need to change, like additional commas, and stuff which is actually not correct, like hyphenating "rate limiting". Also can you confirm that you didn't use any "AI" tooling for this PR? Cheers!

[jimt]

OK.

No AI tooling.

[tsmethurst]

Thanks!