Refresh markdownlint JSON schema (#2038)
Refresh markdownlint JSON schema (#2038)

* Use JSON schema version authored by DavidAnson:
- optimize schema by removing code duplication

* Update markdownlint schema:
- upgrade to 7 draft
- restrict integer values to be greater than 0

* Replace exclusiveMaximum with exclusiveMinimum
schemastore/schemastore,schemastore/schemastore