* feat(docker): Add image layers handler
* Remove unnecessary BadgenError import
* Add metadataHandler and refactor code
* Separate the layers and metadata handlers
Separate the layers and metadata handlers and remove 'metadata' from the layers path.
* revert subject/label to static descriptive text
* Move manifest error checking logic into libs\docker.ts
Move manifest error checking logic into libs\docker.ts to clean up api\docker.ts
* Replace 'throw new BadenError' with grey error badge
Replace 'throw new BadenError' with grey error badge