Adding section links to calling events and updating descriptions

[SevenZeroThree]

• Added section links for the voice and video calling events
  • Each event in the Event Types table now links directly to the corresponding event data section
• Updated descriptions of the following voice and video events to better describe when they are raised
  • Microsoft.Communication.CallParticipantAdded
  • Microsoft.Communication.CallParticipantRemoved
• Minor punctuation updates for chat events

[SevenZeroThree]

@microsoft-github-policy-service agree

[prmerger-automator[bot]]

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

[learn-build-service-prod[bot]]

Learn Build status updates of commit 747b069:

:white_check_mark: Validation status: passed

File	Status	Preview URL	Details
articles/event-grid/communication-services-chat-events.md	:white_check_mark:Succeeded
articles/event-grid/communication-services-voice-video-events.md	:white_check_mark:Succeeded

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[spelluru]

sign-off

[prmerger-automator[bot]]

Invalid command: '#sign-off'. Only the assigned author of one or more file in this PR can sign off. @VikramDhumal

[spelluru]

@VikramDhumal - Please review the changes and enter #sign-off to sign off on the changes. Thanks.

[Court72]

label:"aq-pr-triaged"

@MicrosoftDocs/public-repo-pr-review-team

[spelluru]

@Court72 - Please merge this PR. I am the content dev for the service: Azure Event Grid. Thanks.