Add crumtrail to command pages.

[savente93]

Currently it is a bit hard to navigate around the docs vertically. for example let's say I just searched for path expand and it's close but not exactly want I want. I want to look around the other path subcommands to see if I can see something that works better. currently there is no way to navigate up one part. This makes it even harder if it's not clear which subsection something is under (e.g. get I for the life of me cannot find it's parent page). not being able to navigate up in the tree makes navigation very difficult imo

[NotTheDr01ds]

This would be useful. Unfortunately the default Vuepress theme doesn't support breadcrumbs, so it would involve either changing to a theme with that feature or adding it at the theme level, I believe.

Also problematic is that there really isn't a single "parent" page for the commands themselves. They are auto-generated into /commands/docs/<command>, the categories indices are auto-generated into /commands/categories/<category>, and then master index of all commands is auto-generated at /commands. Is the "parent" page the "Category" or the main "Index"? When visiting a command from a search result, there's really no way for the SSG to know in order to add a breadcrumb "up".