feat(parser): add schema support for API Gateway WebSocket events

[VatsalGoel3]

Summary

Changes

Added schema support for API Gateway WebSocket events to the Parser utility.

This PR introduces a new schema named APIGatewayProxyWebsocketEventSchema under packages/parser/src/schemas/api-gateway-websocket.ts. It enables developers to validate and parse WebSocket Lambda events using @aws-lambda-powertools/parser.

Additionally:

• Added test event file at packages/parser/tests/events/apigw-websocket/connectEvent.json
• Added corresponding unit tests in packages/parser/tests/unit/schema/apigw-websocket.test.ts using the getTestEvent utility
• Schema supports all documented fields including headers, multiValueHeaders, queryStringParameters, stageVariables, requestContext, and body

This schema follows the same structure as other API Gateway events and enables first-class support for $connect, $disconnect, and $message WebSocket routes in Lambda.

Please add the issue number below, if no issue is present the PR might get blocked and not be reviewed

Issue number: closes #3787

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[dreamorosi]

Thanks for the PR!

I've left a couple minor comments but the PR looks good. Can you also add the new schema to the table in docs/utilities/parser.md here.

[VatsalGoel3]

@dreamorosi, I have made the required changes

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[dreamorosi]

Thanks for the PR!