Add GitHub Models AI backend script (via Copilot subscription)

[nagelp]

This adds a new script that integrates GitHub Models as an AI backend for QOwnNotes, allowing users to access AI models through their GitHub Copilot subscription via the GitHub Models inference API.

Features:

• Supports a wide range of models including GPT-4o, GPT-4.1, GPT-5, o1/o3/o4, DeepSeek, Llama 4, Grok 3, Mistral, and Phi-4
• Uses the openAiBackendsHook to register as an AI backend
• Requires only a GitHub Personal Access Token with 'Models: Read' permission

Setup:

1. Install the script in QOwnNotes
2. Enter a GitHub Personal Access Token in the script settings
3. Select 'GitHub' as the AI backend and one of the AI models, e.g. gpt-5

[pbek]

Thank you for the addition! I always thought you need to have something like https://github.com/ericc-ch/copilot-api to access GitHub Copilot via OpenAI API! 🤔 And you are just doing that via https://models.inference.ai.azure.com/chat/completions...