Example storyline overview in Airflow core docs

### Description As described in https://cwiki.apache.org/confluence/display/AIRFLOW/Examples+Refurbish New examples are made including tutorials. This should be weaved into the general Airflow docs in the howto section thus people can see, find and learn from the examples ### Use case/motivation Airflow Examples have been grown in number and focus over the past years. They purpose multiple things: Serve as tutorials to learn Airflow DAG implementation Serve with code snippets for documentation Serve for testing the setup (some) service for CI integration testing Some example DAGs are in a good quality, some are not following best practices. Current examples do not follow a structure. There are example DAGs contained in the Airflow core (currently pushed to standard provider/example_dags) as well as there are more examples in other providers. But examples from other providers are lot loaded automatically. So in the [Airflow 3 Dev Calls](https://cwiki.apache.org/confluence/display/AIRFLOW/Airflow+3+Dev+call%3A+Meeting+Notes#Airflow3Devcall:MeetingNotes-22May2025) there was a demand named to clean-up and optimize example DAGs. ### Related issues _No response_ ### Are you willing to submit a PR? - [ ] Yes I am willing to submit a PR! ### Code of Conduct - [x] I agree to follow this project's [Code of Conduct](https://github.com/apache/airflow/blob/main/CODE_OF_CONDUCT.md)