I added a scroll to top button which enhances user experiences by enabling them to quickly go to top of the page when they have many APIs in the page.

Description

I created a component to implement the functionality of the scroll to top and rendered it in the main app. When the user scrolls down the scroll to top icon appears on the bottom right of the page for 3 seconds until the users scrolls again. The button's appearance is consistent with the Swagger UI theme and style.

Fixes #10169

Screenshots (if appropriate):

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.