Fix deeplinking for topbar plugin

[geekingfrog]

Enable deeplinking with the topbar plugin.

Description

Following zyv's workaround I added some logic to change the location.search property on spec change. It's a bit of a hack though.

Motivation and Context

Fixes #3649

How Has This Been Tested?

I haven't found any automated test for the topbar plugin unfortunately.
I have a branch with a modified version of the index.html used for dev where I tested it manually.

I also added a couple of tests around parsing and serialization of window.location.search.

Checklist

My PR contains...

• No code changes (src/ is unmodified: changes to documentation, CI, metadata, etc.)
• Dependency changes (any modification to dependencies in package.json)
• Bug fixes (non-breaking change which fixes an issue)
• Improvements (misc. changes to existing features)
• Features (non-breaking change which adds functionality)

My changes...

• are breaking changes to a public API (config options, System API, major UI change, etc).
• are breaking changes to a private API (Redux, component props, utility functions, etc.).
• are breaking changes to a developer API (npm script behavior changes, new dev system dependencies, etc).
• are not breaking changes.

Documentation

• My changes do not require a change to the project documentation.
• My changes require a change to the project documentation.
• If yes to above: I have updated the documentation accordingly.

Automated tests

• My changes can not or do not need to be tested.
• My changes can and should be tested by unit and/or integration tests.
• [] If yes to above: I have added tests to cover my changes. [Only partly]
• If yes to above: I have taken care to cover edge cases in my tests.
• All new and existing tests passed.

[OisinKyne]

Hey @shockey, is this likely to be included in a future release? I could do with this fix but am avoiding forking the repository and merging/building swagger-ui myself because of the inconvenience it would cause in the long run.

[shockey]

LGTM

[shockey]

thanks, @geekingfrog!

[shockey]

@OisinKyne, this will be included in the next release we do 😄