Create Task SDK docs

[sunank200]

Description

The Task SDK currently has no dedicated documentation within the Airflow docs site or anywhere. We need to create a new site for “Task SDK” that covers installation, decorators, core classes (BaseOperator, Sensor, XComArg, etc.), definitions (assets, types), execution-time components (Supervisor, TaskRunner, Context), I/O helpers, and the API client.

Use case/motivation

• Users installing apache-airflow-task-sdk need a clear “Getting Started” guide.
• Developers need reference pages for decorators (@task, @dag, etc.) and core classes.
• Runtime engineers need documentation on Supervisor/TaskRunner/Context for debugging and extension.
• Without docs, adoption of the standalone Task SDK is hampered and contributions become more error-prone.

Related issues

• AIP-72: Task Execution Interface (Task SDK) design proposal.
• No existing GitHub issue explicitly tracking Task SDK docs creation.

Are you willing to submit a PR?

• Yes I am willing to submit a PR!

Code of Conduct

• I agree to follow this project's Code of Conduct