Make validation error messages from circe-json-schema nicer

[jisantuc]

Improvement

The validate call from json schema resolved from URLs produces really unfriendly strings:

      [
            "#",
            "#",
            "#",
            "#/stac_extensions",
            "#/type",
            "#/stac_extensions"
        ]

To the extent possible, these should be improved so they're nicer for humans.