Feature: Sidebar to group, navigate and search

Hi everyone,

Is your feature request related to a problem?

When working with APIs that have lots of methods it's hard to navigate the page to test different methods since users usually need to scroll up/down a lot.

Describe the solution you'd like

Add an optional sidebar which supports grouping, navigation and searching of api methods, tags, etc.
I had a look at an old issue https://github.com/swagger-api/swagger-ui/issues/4373 describing the same problem with the UI so I'm opening another one to understand whether the swagger-ui team is interested in this feature.
I also see there is a related open issue in the swagger-editor repository: https://github.com/swagger-api/swagger-editor/issues/3269

Describe alternatives you've considered

Other API documentation solutions have this feature.
E.g. Redoc: https://redocly.github.io/redoc/

Will this feature eventually make its way in the swagger-ui repository?

The issue does not name files, tests, or an entry point. Start by reviewing the related Swagger UI issue 4373 and Swagger Editor issue 3269, then inspect the existing API documentation navigation. Done means an optional sidebar can group, navigate, and search API methods and tags.