MM-22679 - Update example plugin documentation (#13944)

Automatic Merge

plugin/example_hello_world_test.go

@@ -10,10 +10,13 @@ import (
 	"github.com/mattermost/mattermost-server/v5/plugin"
 )
 
+// HelloWorldPlugin implements the interface expected by the Mattermost server to communicate
+// between the server and plugin processes.
 type HelloWorldPlugin struct {
 	plugin.MattermostPlugin
 }
 
+// ServeHTTP demonstrates a plugin that handles HTTP requests by greeting the world.
 func (p *HelloWorldPlugin) ServeHTTP(c *plugin.Context, w http.ResponseWriter, r *http.Request) {
 	fmt.Fprint(w, "Hello, world!")
 }