chore: rename keystone to draft

Rename the module, CLI command name, and all references from
keystone/basalt to draft, and fix the stale build/README content
found along the way.

cmd/handler.go

@@ -23,7 +23,7 @@ func init() {
 var handlerCmd = &cobra.Command{
 	Use:   "handler",
 	Short: "Create a new handler",
-	Long:  `Create a new handler for your Keystone project.`,
+	Long:  `Create a new handler for your Draft project.`,
 	Run:   genHandler,
 }