use spawn() instead of spawnSync()

[yegor256]

At the moment, we have this code in mvnw.js:

  const result = spawnSync(
    bin,
    process.platform == 'win32' ? params.map((p) => `"${p}"`) : params,
    {
      cwd: home,
      stdio: 'inherit',
      shell: shell(),
    }
  );

It runs a provided bin command and returns its exit code. While it runs, we have no control. I suggest to replace spawnSync with spawn and check the status of the running command asynchronously. While waiting for the command to finish we can list all files in the directory and print its total count. This printing will help the user who is waiting to get a better feeling about the process.

[yegor256]

@volodya-lombrozo can you help with this?

[volodya-lombrozo]

@yegor256 I can try, just assign issue to me