message: Clarification on when field value source is valid in parseSQL
diff: @@ -122,6 +122,8 @@ Output (`RuleGroupTypeIC`):
  When the `fields` option (which accepts the same types as the [`fields` prop](./querybuilder#fields)) is provided, and _only_ if it is provided, then `parseSQL` will validate clauses that have a field identifier to the right of the operator instead of a primitive value. A `getValueSources` function can also be provided to help validate rules.
  +In order for such a rule to be considered valid, either the `getValueSources` return value, the field's `valueSources` property return value, or the field's `valueSources` property itself must be an array that includes the string "field".
  +
  ```ts
  parseSQL(`SELECT * FROM t WHERE firstName = lastName`, {
  fields: [
  