prettier formatting for json files

[bpkroth]

• Add Makefile format target rules to reformat *.json and *.jsonc files.
• Add Makefile check target rules to check the format of json files.
• Add pre-commit config hooks using either prettier or pretty-format-json
• Require those rules and reformat json files.
  • Rename *.jsonc files to *.mlos.jsonc files.
    Might as well do this at the same time we're rewriting all files.
    See Also: external config improvements #522

[bpkroth]

Could also make use of pretty-format-json hook in our new .pre-commit-config.yaml.

See: #904