Add guide for helping with created_at and updated_at timestamps

Let’s add a guide to help users model created_at and updated_at timestamps.

For created_at a default value of now() works. For updated_at a trigger on the lines of: https://x-team.com/blog/automatic-timestamps-with-postgresql/

[hrmoller]

Thanks for the Frequently used columns feature👍 However, it would be super nice if this feature was also available on the Modify-tab so it can be used on tables already created.

[sebastianmacias]

created_at and updated_at automatic timestamps are so commonly used. I think there should be an option to set the timestamp field to automatically handle this when creating the schema.

By the way the link posted is broken, this is the working link: https://x-team.com/blog/automatic-timestamps-with-postgresql/