Update LICENSE copyright and add AI attribution instructions

[jerrysxie]

This PR applies two org-wide standardisation changes
(ref: OpenDevicePartnership/embedded-rust-template#20):

1. LICENSE – normalise the copyright line to:
   Copyright (c) Open Device Partnership and Contributors

2. .github/copilot-instructions.md – add the Commit Messages and
   AI Attribution sections so every repo carries consistent guidance
   for contributors and AI agents.

[Copilot]

Pull request overview

This PR applies organization-wide standardization updates by normalizing the project’s MIT license copyright line and adding a repository-level Copilot guidance document for consistent commit message and AI attribution practices.

Changes:

• Update the MIT LICENSE copyright line to the org-standard “Open Device Partnership and Contributors”.
• Add .github/copilot-instructions.md with commit message conventions and required AI attribution (Assisted-by) guidance.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
LICENSE	Normalizes the copyright holder line to the org standard.
.github/copilot-instructions.md	Adds standardized commit message and AI attribution instructions for contributors/agents.

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