Display dbt-labs/dbt_external_tables configurations in source table details.

### Describe the feature

Source configurations under `external:` using the package [dbt-labs/dbt_external_tables](https://github.com/dbt-labs/dbt-external-tables) are not visible in the documentation.

This information is very valuable to locate the original file(s) behind an external table.

This information is available in the manifest.json.

It could be nested within the source table details, similarly to Extended Stats.

### Describe alternatives you've considered

Duplicating the information in a big description, either manually or programmatically.

### Additional context

This feature is specific to the use of the package [dbt-labs/dbt_external_tables](https://github.com/dbt-labs/dbt-external-tables) and should have no impact on other sources.

### Who will this benefit?

- Organizations using [dbt-labs/dbt_external_tables].
- Analysts and Product Managers looking for upstream sources.
- Engineers saving time on documentation maintenance and answering simple questions.

### Are you interested in contributing this feature?

Yes, I am about to send a PR.