/conf/custom-functions/

/conf/custom-functions/declaration-not-array: A functions value that is a string is invalid.
/conf/custom-functions/declaration-valid: functions as an array of strings with a functionsDir string is valid.
/conf/custom-functions/invoke: The function receives the value and the options, and each problem it returns becomes a result with its message.
/conf/custom-functions/javascript-promise: A function that returns a promise is awaited, and the problems it resolves to are reported.
/conf/custom-functions/load-custom-dir: With functionsDir, the function is loaded from that directory.
/conf/custom-functions/load-default-dir: A function named in functions is loaded from functions/<name>.js next to the ruleset.
/conf/custom-functions/missing: A ruleset naming a function whose file does not exist is rejected.
/conf/custom-functions/present: A ruleset naming a function whose file exists is loaded and the function runs.
/conf/custom-functions/problem-path: A problem with a path is reported there; one whose path is not in the document is reported at the root.
/conf/custom-functions/returns-nothing: A function that returns nothing reports no problems, while one that returns a problem does.