Convert repo to using yarn for improved dependency management and to use customized dependencies

[michaeljwiebe]

Description

I was attempting to use a customized version of the Swagger-UI package in my Swagger Editor but was unable to do so using npm. Switching over to yarn resolved the issue for me. Yarn doesn't require special flags to install locally like npm does (see --legacy-peer-deps).

Motivation and Context

Fixes #5000 - This PR allows me to link my local swagger-editor to a customized version of swagger-ui that I have locally using the local relative path to the repo as the version in my package.json. See package.json:

How Has This Been Tested?

I ran yarn test and have built and ran locally and verified that the swagger-editor works and swagger-ui is importing correctly.

Screenshots (if appropriate):

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.
• If yes to above: I have taken care to cover edge cases in my tests.
• All new and existing tests passed.