transaction with watch example added

[sailingwithsandeep]

Description

#2280

My pull request is about creating an example of redis transactions which shows a sample code that runs in isolated connection and provides optimistic locking with check-and-set (CAS) behavior.

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Checklist

• [] Does npm test pass with this change (including linting)?
• [] Is the new or changed code fully tested?
• [] Is a documentation update included (if this change modifies existing APIs, or introduces new ones)?

[SuzeShardlow]

Thanks for your PR @sailingwithsandeep, we will check it out :)

[simonprickett]

Hi there @sailingwithsandeep I'm unable to run this:

examples $ node transaction-with-watch.js
Error: ReferenceError: redis is not defined

Please can you check into this and make sure that the code runs. Thanks.