Maintenance: PR Clean Up

Guide for Cleaning up a PR

We have situation where someone opens a PR and they are not able to do some clean-ups before it's landed.

Steps:

Make sure your local master is up to date with the origin/master, origin being validatorjs/validator.js
Create a remote pointing to the repo where the PR originated from, e.g. for the case of PR#923:
```
$ git remote add other [email protected]:odrzutowiec/validator.js.git
```

Checkout a new branch off master, can name it chore-clean-#<pr-id>
Fetch the work from the remote branch (will not always be master, depends on what the author called it), e.g.
```
 $ git fetch other master
```
Merge the fetched branch and fix merge conflicts if any (NB: using -X ours, then add back their work manually, e.g.
```
$ git merge other/master -X ours
```
Make all the necessary changes, run tests and commit the work.
To get the users email address to be used in the Co-authored-by, you can go back to the PR and click on any of their commits:
- On the browser's address bar, add .patch on the URL and click enter.
- You should see details of their email or the privacy-enhanced one by Github in the From: field.

In your commit body, remember to add:

Co-authored-by: name <[email protected]>

closes #<pr-id> #<original-issue-id-if-any>

Push the new work to your remote (the fork on your GH profile), eg.
```
$ git push prof chore-clean-#923
```
Go to GH and create a new PR, linking it up with the old PR.