Please include os-caddy-plugin into OPNsense plugins

[Monviech]

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

Describe the solution you'd like
Adding the os-caddy-plugin source code to the opnsense-plugins so the package is built and included in the official repository.

• Integration Tracking Issue: Integration of Caddy into OPNsense repository Monviech/os-caddy-plugin#102

• The caddy binary was included into the OPNsense Tools and the built is successful: opnsense/tools@a555d25

• Plugin Source Code: https://github.com/Monviech/os-caddy-plugin/tree/1ec6614b908c2a4638719fe9dab58d2a84a729a5/usr/plugins/devel/caddy

• Plugin Documentation: https://github.com/Monviech/os-caddy-plugin/blob/1ec6614b908c2a4638719fe9dab58d2a84a729a5/README.md

Describe alternatives you've considered
Keeping the plugin in my separate repository.

Additional context
If it's added, maybe the POST_INSTALL script should be adjusted to check if my repository exists on the OPNsense, and then delete it so the caddy binary and os-caddy package are then always collected from the main OPNsense repository instead.

If there are any things that need to be changed and fixed, please tell me about them. Though things are working as expected and a lot of people use the plugin already, I would like to keep it the way it is right now so that the migration from my repository to OPNsense repository is as transparent as possible without having any breakage.