Stylize individual breadcrumbs based on directory type

[jwodder]

Suggested by @yarikoptic in #14 (comment).

Breadcrumbs should be styled (usually just with different colors) based on the type of what they point to:

• Server root
• /dandisets/ & /zarrs/
• /dandisets/:id/
• /dandisets/:id/draft/, /dandisets/:id/latest/, and /dandisets/:id/releases/:version/
  • Separate style for /dandisets/:id/releases/?
• Asset folders
• Zarr assets (including checksum manifests presented as Zarrs)
• Folders inside Zarrs (including under checksum manifests)
• Directories between /zarrs/ and checksum manifests