feat: add sub-document pagination (feats: #174)

[lau1944]

Add a new feature for sub-document pagination #174

[aravindnc]

@lau1944 Excellent! I will review and merge over this weekend.

[lau1944]

Cool! Thank you.
If any issue related to this in the future, feel free to mention me, I will look into it.

[aravindnc]

@lau1944 I've moved your method to a new file.
I've commented out below code from pagination-subdocs.js

  // options = Object.assign(options, {
  //     customLabels: defaultOptions.customLabels,
  // });

Please see if you can get the default options from the index file easily.

[lau1944]

@aravindnc Looks good to me!
After took a look on the paginate-subdoc method, I only use projection field in the default options object, so I don't think default options is needed in this function.

[lau1944]

#176