updated plugin for Caddy 2.0.0

[rgdev]

Here's an update of the plugin for the new Caddy 2.0.0 version (certmagic 0.10.12). changes :

• added main.go with the proper Caddy 2 plugin implementation to register a storage plugin
• updated dependencies
• updated go version to 1.14
• updated README with updated instructions
• updated the Dockerfile to use the official caddy builder image

I recommend making a copy of the current master to a "caddy1" branch, check out the "older versions" of the README.md to understand my reasoning. Also the module name needs to be changed in the go.mod & dockerfile to match your github repo.

[pteich]

Many thanks for your PR! I'll have a look. I always wanted to do this but could not because lack of time.

[zenpan]

Per @rgdev suggestion, the go.mod and Dockerfile need to be changed to reference this github repo instead of Raphael's. Otherwise it fails to build. I can probably fork and point to my own to resolve building new Docker images with caddy-builder but thought you might want to fix this for others.

[pteich]

Fixed in master

[mholt]

Great! I have added this plugin to https://caddy.community/t/list-of-caddy-2-modules/7839 (until our new website allows plugin registration like the old website).