Allow tighter integration with `fzf`

Would be nice that instead of directly copying passwords with `fzf`, there was a way to invoke `1pass` to display the details (overview) of the login/note/etc in the fzf preview pane.

**Rationale**
1. I sometimes have logins/notes/etc. in multiple vaults that have similar or same name, and are for different users.
2. Currently only thing that can be previewed with `1pass` is list of fields available on the item and the associated password (or note content). The latter is dangerous to be displayed due to over-the-sholder eavesdropping, and the former is not very usable if we need to distinguish between users or URLs of the items.
3. I could use `op` directly for that, but if `1pass` already provides a caching layer, I'd prefer to use it. Also, I like having a single interface authenticating me.