www/caddy: [WIP] v1.5.6

[Monviech]

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• [x] I have read the contributing guide lines at https://github.com/opnsense/plugins/blob/master/CONTRIBUTING.md
• [x] I have searched the existing issues, open and closed, and I'm convinced that mine is new.
• [x] When the request is meant for an existing plugin, I've added its name to the title.

WIP for os-caddy v1.5.6:

• [ ] https://github.com/opnsense/plugins/pull/3961

Changelog:

... not yet done cause version is not finished yet.

Waiting for caddy binary v2.8.0 to be released and available upstream before pushing this release further.

[Monviech]

Gonna be in 1.5.5 so closing it.