Set global silent status

By setting the silent state with this function, you can control silent and silent! messages as follows.

import { Denops } from "../mod.ts";
import { echo, echoerr, setSilent } from "../helper/mod.ts";

export async function main(denops: Denops): Promise<void> {
  // Because silent is "silent!", `echo` and `echoerr` doesn't show messages.
  setSilent(denops, "silent!");
  await echo(denops, "Hello\nWorld!");
  await echoerr(denops, "This is error message");

  // Because silent is "silent", `echo` doesn't show messages.
  setSilent(denops, "silent");
  await echo(denops, "Hello\nWorld!");
  await echoerr(denops, "This is error message");

  // Because silent is "", both show messages.
  setSilent(denops, "");
  await echo(denops, "Hello\nWorld!");
  await echoerr(denops, "This is error message");
}