fix meetingStart and meetingEnd casing bug & add meetings sample

[lilyydu]

similiar to: microsoft/teams.net#198 and microsoft/teams.ts#434

fixes: #245

[Copilot]

Pull request overview

This PR fixes a critical bug where meeting start and end event activities failed validation due to incorrect field name casing. The Microsoft Teams API sends these fields in PascalCase format (e.g., MeetingType, JoinUrl) rather than camelCase, causing validation errors. The fix updates the field definitions to use PascalCase directly instead of relying on the automatic snake_case to camelCase conversion. Additionally, the PR makes the role field in MeetingParticipantInfo optional to match the actual API behavior, and adds a new meetings sample application to demonstrate usage.

Changes:

• Fixed field name casing in MeetingStartEventValue and MeetingEndEventValue from snake_case to PascalCase to match Teams API
• Made the role field optional in MeetingParticipantInfo class
• Added new meetings example application demonstrating meeting event handlers

Reviewed changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
packages/api/src/microsoft_teams/api/activities/event/meeting_start.py	Updated field names from snake_case to PascalCase (Id, MeetingType, JoinUrl, Title, StartTime) to match Teams API format
packages/api/src/microsoft_teams/api/activities/event/meeting_end.py	Updated field names from snake_case to PascalCase (Id, MeetingType, JoinUrl, Title, EndTime) to match Teams API format
packages/api/src/microsoft_teams/api/activities/event/meeting_participant.py	Added Optional import and made role field optional with default None value
examples/meetings/src/main.py	New example demonstrating meeting event handlers for start, end, participant join/leave events
examples/meetings/pyproject.toml	Configuration for new meetings example package
examples/meetings/README.md	Documentation for meetings example with manifest requirements
README.md	Added link to new meetings example in the examples list