feat: PE-1075: Update the dev-cookbook send message example to be @brightsign/messageport

[blshukla]

📝 Description

• Update BSMessagePort -> @brightsign/messageport in the HTML file.
• Fix undefined error with msg.data

Issue: PE-1075

✔️ Dev Complete Checklist

• PR template filled out
• Change is tested by submitter
• PR follows all linting and coding standards
• Github Issue exists (if applicable)
• Team member has been assigned
• At least one commit message is in Conventional Commit format

[Copilot]

Pull Request Overview

This PR updates the send-plugin-message example to use the @brightsign/messageport package instead of the deprecated BSMessagePort API, and fixes a bug where message data was incorrectly accessed via msg.data instead of msg directly.

• Updates the HTML file to use the modern @brightsign/messageport module instead of the deprecated BSMessagePort
• Fixes incorrect message data access pattern by changing msg.data["property"] to msg["property"]
• Adds documentation for a new MessagePort example in the README

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
examples/send-plugin-message/pluginMessageApp.html	Updates to use @brightsign/messageport module and fixes message data access pattern
examples/send-plugin-message/plugin-message-transfer.bpfx	Updates project metadata including version, timestamps, and file paths
examples/README.md	Adds documentation for the MessagePort example

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[jdmedlin1]

This is great. Thanks!