UI fails to load when navigating directly to a page more than one directory deep

[wyattanderson]

Describe the bug

As far as I can tell, starting with 2.10.0, assets in the returned HTML are requested from ./_app instead of /_app. When a user navigates directly to a route that is more than one directory deep, the assets fail to load because the browser requests them relative to the page URL.

For instance, if a user clicks an external link like http://localhost:8080/namespaces/default/workflows or refreshes the browser while on this page, the browser tries to request assets from http://localhost:8080/namespaces/default/_app/immutable/start-ca935cf5.js instead of http://localhost:8080/_app/immutable/start-ca935cf5.js, and the page never loads.

To Reproduce
Steps to reproduce the behavior:

1. Start a local cluster with docker-compose up
2. Navigate to http://localhost:8080/, which the app will rewrite to http://localhost:8080/namespaces/default/workflows
3. Refresh the page
4. The page fails to load