Build-in notes for pins.

It might be out of the scope but it would be great if pins could have notes with them.

Countless times I wondered what the file is, and what it does in IPFS, it is even worst if it is only plain file and not directory, so here is my proposal.

Optional notes that can be added while pinning (in similar fashion pin-bot has it), if file is being added also allow to specify note for the pin and if not specified use full file path (or state that it was stdin) with timestamp (ISO 8601).