add `trigger_dbt_cli_command` example to docs

[James Bada Sopkin]

Expectation / Proposal

I think it would be helpful to have a section(or subsection) with a code snippet example and explanation of the trigger_dbt_cli_command. It is helpful for running a one off dbt cli command, but I had to read the prefect-dbt/cli/commands.py file to figure out what it was and how to use it. I'm willing to contribute this to the readme.

Traceback / Example

• I would like to help contribute a pull request to resolve this!