Add "Next Steps" doc/epilog at the end of running init and build

[kaxil]

Similar to the following, there should be a "Next Steps" doc printed after someone runs airflowctl build
to show them the following and their usage:

For init:

• settings.yaml (airflow_version and python_version)
• requirements.txt
• dags directory

For build:

• Running DAGs
• Activating venv and running airflow commands
• Changing executor (and configuring postgres) (probably ??)

airflowctl/airflowctl/cli.py

Lines 431 to 441 in e4f8fe1

	next_steps += f"""
	* You can now run all the "airflow" commands in your terminal. For example:
	[bold blue]$ airflow version[/bold blue]
	* Run Apache Airflow in standalone mode using the following command:
	[bold blue]$ airflow standalone[/bold blue]
	* Access the Airflow UI in your web browser at: [bold cyan]http://localhost:8080[/bold cyan]
	For more information and guidance, please refer to the Apache Airflow documentation:
	[bold cyan]https://airflow.apache.org/docs/apache-airflow/{version}/[/bold cyan]

[anthonysocks]

@kaxil I can take this (:

[kaxil]

Assigned it to you @anthonysocks :)