Add spinner module

[mvirgil]

Example usage:

        const spinner = createSpinner();
        spinner.start('Testing...');
        setTimeout(() => {
          spinner.interrupt(() => {
            console.log('Safely log during an active spinner using interrupt()');
          });
        }, 3000);
        setTimeout(() => {
          spinner.interrupt(() => {
            console.log('Safely log during an active spinner using interrupt() #2');
            console.error('Safely log during an active spinner using interrupt() #3');
          });
        }, 4000);
        setTimeout(() => {
          spinner.stop();
        }, 5000);
        setTimeout(() => {
          spinner.start('Reuse the same object');
        }, 6000);
        setTimeout(() => {
          spinner.stop();
          console.log('Done');
        }, 7000);

To use this with promises / async-await:

try {
  spinner.start('Waiting...');
  await someApiCall();
catch (e) {
  handleSomeError(e)
} finally {
  spinner.stop()
}

try {
  // some big try-catch
  spinner.start('with async...');
  await mockAsyncWork()
      .finally(() => spinner.stop());
  console.log('success!');
   // ...
} catch (e) {
   // ... normal error-handling code
}

We can add more helpers to this as-needed, in case we find it is clunky to use with our
actions and/or our logging needs. (Ex: expose something similar to oraPromise(), or a helper function to create a "spinner-aware" logger)

Uses the default "dots", though you can browse https://jsfiddle.net/sindresorhus/2eLtsbey/embedded/result/ which is a superset of what's available.