allow for secondary bookmarks

[makapuf]

Sometimes I'd like to have lower priority bookmarks by example to keep a bookmark for later viewing or as a low priority alternative to an interesting talk. It would not show as a conflict by example.

[hrw]

Maybe not second bookmarks but priorities.

So I mark "docker python" as primary and "rake for dummies" and "go for mcu" as secondary.

This way I know that "docker python" is one I want to go but it is raining so I go for "go for mcu" as it is dame building as I am.