Add date checked off to meta data

[andybyte]

Is your feature request related to a problem? Please describe.
When I check an item off, I thought that the task would record the date it was checked off. If this is a feature already then I'm not sure how to enable it. Knowing when I did something is sometimes important information in the future.

Describe the solution you'd like
Checking an item as done adds the current date(time?) to the note, either in the body or the metadata. I think metadata would make more sense of course. Or, using a command to mark task as complete does both.

Describe alternatives you've considered
I could write in the date/metadata myself before checking it off but that feels unnecessary.

Additional context
Add any other context or screenshots about the feature request here.

[tgrosinger]

@andybyte, I think adding this to the frontmatter would be reasonable. In the meantime, you can also see when the note was last modified, which for a completed task would often be the date it was checked.