format schema validation errors

Right now they are basically an error json dump.
Do something similar to this: https://github.com/adobe/aio-lib-state/blob/main/lib/utils.js

Start by comparing the current schema-validation error output with the example in lib/utils.js from the linked aio-lib-state repository. Locate the code in this repository that emits the error, then confirm the work is done when validation failures are presented in a similarly readable format rather than as a raw JSON dump.

Written by the indexing model from the issue text.