nginx(role): document arguments in README for better discoverability

Document the role arguments in the README instead of in the
argument_specs for better discoverability and readability.

roles/nginx/meta/argument_specs.yaml

@@ -2,21 +2,14 @@ argument_specs:
   main:
     options:
       nginx__deploy_redirect_conf:
-        description: >-
-          Whether or not to deploy a `redirect.conf` to
-          `/etc/nginx/conf.d/redirect.conf`.
         type: bool
         required: false
         default: true
       nginx__deploy_tls_conf:
-        description: >-
-          Whether or not to deploy a `tls.conf` to `/etc/nginx/conf.d/tls.conf`.
         type: bool
         required: false
         default: true
       nginx__deploy_logging_conf:
-        description: >-
-          Whether or not to deploy a `logging.conf` to `/etc/nginx/conf.d/logging.conf`.
         type: bool
         required: false
         default: true
@@ -28,34 +21,16 @@ argument_specs:
         default: [ ]
         options:
           name:
-            description: >-
-              The name of the configuration file, where the configuration should
-              be deployed to. The file will be placed under `/etc/nginx/conf.d/`
-              and `.conf` will be appended to the given name. So in the end the
-              path will be like this: `/etc/nginx/conf.d/\{\{ name \}\}.conf`.
-              Note that the names `tls` and `redirect` aren't allowed.
             type: str
             required: true
           content:
-            description: The content of the configuration.
             type: str
             required: true
       nginx__use_custom_nginx_conf:
-        description: >-
-          Whether or not to use a custom `/etc/nginx/nginx.conf`. If set to
-          true, you must provide a custom `nginx.conf` via
-          `nginx__custom_nginx_conf`.
         type: bool
         required: false
         default: false
       nginx__custom_nginx_conf:
-        description: >-
-          The value for a `nginx.conf` to be placed at `/etc/nginx/nginx.conf`.
-          You must set `nginx__use_custom_nginx_conf` to true for this value to
-          be used.
-          You should probably make sure that your custom `nginx.conf` still
-          includes `/etc/nginx/conf.d/*.conf` so that the configuration provided
-          using `nginx__configurations` still work.
         type: str
         required: false
         default: ""