Add example using updated_at with check strategy

[mirnawong1]

Contributions

• I have read the contribution docs, and understand what's expected of me.

Link to the page on docs.getdbt.com requiring updates

Based on community slack convo, having an updated_at example w the check strategy would be useful.

From teh docs:

For the check strategy, the current timestamp is used to populate each column. If configured, the check strategy uses the updated_at column instead, as with the timestamp strategy.

From user:

the source code confirms that effectively the check strategy picks up the updated_at column (and if not present, it falls back to using a timestamp).

What part(s) of the page would you like to see updated?

https://docs.getdbt.com/reference/resource-configs/updated_at

Additional information

No response