Add {{obsidianTasksCancelledDate}} to the placeholders

[ChayseSmith]

Archiver is fantastic and I'm loving it, but I'm noticing I have a lot of "cancelled" tasks that don't get a "completed" date.

I was wondering if you could include other types of placeholders that would exist on a task for the archiver to use, such as Cancelled Date, Scheduled Date, Status name/symbol etc

[ivan-lednev]

Hello, @ChayseSmith! I'm not working on this plugin right now, but I might implement it some day. Of course, I'll gladly accept a pull-request.