Move Schema to a file and publish it in Schema Store

[yahavi]

Is your feature request related to a problem? Please describe.
Currently, the schema exists only in the README. This way it is not testable. Also, users can't verify their own build-infos.

Describe the solution you'd like to see
Move the schema from README to a file.

Describe alternatives you've considered
Nope.

Additional context
File Spec schema and tests examples: https://github.com/jfrog/jfrog-cli/tree/v2/schema
File Spec schema in the SchemaStore: https://raw.githubusercontent.com/jfrog/jfrog-cli/v2/schema/filespec-schema.json