Follow up to remote content browsing ui polish

[akolson]

Summary

This pr fixes is a follow up to #10573 that;

• Corrects the buggy routing implementation on refresh and click back
• Delayed loading state on the Explore libraries page
• Fixes the LibraryPage skipped tests

References

Follow up to #10573

Reviewer guidance

• Explore a particular library. Clicking on the close button (X) at top left should take you back to the previous page. Also, refreshing the page and clicking the same should yield the same result
• A loading state has been added to indicate load of the resources

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Testing checklist

• Contributor has fully tested the PR manually
• If there are any front-end changes, before/after screenshots are included
• Critical user journeys are covered by Gherkin stories
• Critical and brittle code paths are covered by unit tests

PR process

• PR has the correct target branch and milestone
• PR has 'needs review' or 'work-in-progress' label
• If PR is ready for review, a reviewer has been added. (Don't use 'Assignees')
• If this is an important user-facing change, PR or related issue has a 'changelog' label
• If this includes an internal dependency change, a link to the diff is provided

Reviewer checklist

• Automated test coverage is satisfactory
• PR is fully functional
• PR has been tested for accessibility regressions
• External dependency files were updated if necessary (yarn and pip)
• Documentation is updated
• Contributor is in AUTHORS.md

[github-actions]

Build Artifacts

Asset type	Download link
PEX file	kolibri-0.16.0a12.dev0_git.257.g53165686.pex
Windows Installer (EXE)	kolibri-0.16.0a12.dev0+git.257.g53165686-unsigned.exe
Debian Package	kolibri_0.16.0a12.dev0+git.257.g53165686-0ubuntu1_all.deb
Mac Installer (DMG)	kolibri-0.16.0a12.dev0+git.257.g53165686-0.3.0.dmg
Source Tarball	kolibri-0.16.0a12.dev0+git.257.g53165686.tar.gz
WHL file	kolibri-0.16.0a12.dev0+git.257.g53165686-py2.py3-none-any.whl

[marcellamaki]

I think this is okay to merge for the bug bash, and as I don't think there's anything blocking. The back button and refresh issues seem to be resolved (if I am understanding them correctly, at least).

As for the loading state, I think there is still something to be sorted out with the ui of the loading state, but I think there might be intersections with @nucleogenesis's work on the loading state cleanup, so I feel okay with merging and seeing once that is in what else needs to be sorted out, rather than duplicating or conflicting efforts.