Collapse paths for files deep in subfolders

[krassowski]

References

Fixes #515. The full path is displayed upon hovering over the collapsed path:

Code changes

• Added react test for get_breadcrumbs
• Added code to collapse the breadcrumb path if more than three parts; assumes forward slash as the paths are normalized at this point

User-facing changes

Before:

After:

Before:

After:

Backwards-incompatible changes

Adds a "collapse" toggle to get_breadcrumbs

Chores

• linted
• tested
• documented
• changelog entry