Expose the AuditQueue instance, add the isRunning property to it

README.MD

@@ -28,6 +28,7 @@ When adding agnostic-axe to your project, be sure to only import it in your deve
 Accepts one parameter:
 
 - `violationsCallback` (required). A function that is invoked with an array of violations, as reported by [axe-core](https://github.com/dequelabs/axe-core). To log violations to the console, simply pass the `logViolations` function exported by this module.
+- `auditQueueCallback` (optional). A function that is invoked with an instance of `AuditQueue` to be able to access its state (i.e., the `isRunning` property).
 
 ### AxeObserver.observe
 

src/AuditQueue.mjs

@@ -55,4 +55,7 @@ export default class AuditQueue {
       }
     })
   }
+  get isRunning() {
+    return this._isRunning
+  }
 }

src/AxeObserver.mjs

@@ -24,7 +24,7 @@ const SharedAuditQueue = new AuditQueue()
 // The AxeObserver class takes a violationsCallback, which is invoked with an
 // array of observed violations.
 export default class AxeObserver {
-  constructor(violationsCallback) {
+  constructor(violationsCallback, auditQueueCallback) {
     if (typeof violationsCallback !== 'function') {
       throw new Error(
         'The AxeObserver constructor requires a violationsCallback'
@@ -42,6 +42,10 @@ export default class AxeObserver {
         this._auditNode(mutationRecord.target)
       })
     })
+
+    if (auditQueueCallback) {
+      auditQueueCallback(SharedAuditQueue)
+    }
   }
   observe(targetNode) {
     if (!targetNode) {