jsdoc,comment: Copy 2 tiny additions from my fork (#1975)

* comment: Copy in a comment from my fork, explaining regex

* jsdoc: Document Grouper.reverse

Author: claremacrae

src/Query/Filter/Field.ts

@@ -342,6 +342,7 @@ export abstract class Field {
             throw Error(`grouperRegExp() unimplemented for ${this.fieldNameSingular()}`);
         }
 
+        // The $ at end is required to distinguish between group by status and status.name
         return new RegExp(`^group by ${this.fieldNameSingularEscaped()}( reverse)?$`);
     }
 

src/Query/Grouper.ts

@@ -34,6 +34,9 @@ export class Grouper {
      */
     public readonly grouper: GrouperFunction;
 
+    /**
+     * Whether the headings for this group should be reversed.
+     */
     public readonly reverse: boolean;
 
     constructor(property: string, grouper: GrouperFunction, reverse: boolean) {