Update the steps to use webpack

[JoshuaLai]

When testing the MSDocs, following the steps in its current state doesn't build as expected.
Taking a look at the quickstart sample, we updated the MSDoc to use webpack to match.
Original quick start that uses webpack here

Updated the MSDoc accordingly.

[prmerger-automator]

@JoshuaLai : Thanks for your contribution! The author(s) and reviewer(s) have been notified to review your proposed change. @ProbablePrime

[learn-build-service-prod]

Learn Build status updates of commit d91c178:

✅ Validation status: passed

File	Status	Preview URL	Details
articles/communication-services/quickstarts/chat/includes/chat-js.md	✅Succeeded

For more details, please refer to the build report.

[v-dirichards]

@sroons

Can you review the proposed changes? The original author is no longer with Microsoft.

Important: When the changes are ready for publication, adding a #sign-off comment is the best way to signal that the PR is ready for the review team to merge.

#label:"aq-pr-triaged"
@MicrosoftDocs/public-repo-pr-review-team

[JoshuaLai]

@v-dirichards updating the doc to author @awang119 as she is the new PM who will be driving the Chat initiatives can we update the assignee to her?

[learn-build-service-prod]

Learn Build status updates of commit 0e8a292:

✅ Validation status: passed

File	Status	Preview URL	Details
articles/communication-services/quickstarts/chat/includes/chat-js.md	✅Succeeded

For more details, please refer to the build report.