Add plugin example to extra_runtime_dependencies

lib/puma/dsl.rb

@@ -583,6 +583,8 @@ def lowlevel_error_handler(obj=nil, &block)
     # new Bundler context and thus can float around as the release
     # dictates.
     #
+    # See also: extra_runtime_dependencies
+    #
     # @note This is incompatible with +preload_app!+.
     # @note This is only supported for RubyGems 2.2+
     def prune_bundler(answer=true)
@@ -603,7 +605,7 @@ def raise_exception_on_sigterm(answer=true)
     end
 
     # When using prune_bundler, if extra runtime dependencies need to be loaded to
-    # initialize your app, then this setting can be used.
+    # initialize your app, then this setting can be used. This includes any Puma plugins.
     #
     # Before bundler is pruned, the gem names supplied will be looked up in the bundler
     # context and then loaded again after bundler is pruned.
@@ -612,7 +614,7 @@ def raise_exception_on_sigterm(answer=true)
     # @example
     #   extra_runtime_dependencies ['gem_name_1', 'gem_name_2']
     # @example
-    #   extra_runtime_dependencies ['puma_worker_killer']
+    #   extra_runtime_dependencies ['puma_worker_killer', 'puma-heroku']
     def extra_runtime_dependencies(answer = [])
       @options[:extra_runtime_dependencies] = Array(answer)
     end