add description for call

Author: jkrumbiegel

src/command/call/cmd.ts

@@ -3,6 +3,7 @@ import { engineCommand } from "../../execute/engine.ts";
 
 export const callCommand = new Command()
   .name("call")
+  .description("Access functions of Quarto subsystems such as its rendering engines.")
   .action(() => {
     callCommand.showHelp();
     Deno.exit(1);