feat(external_api) add event with transcription chunks

modules/API/API.js

@@ -1987,6 +1987,20 @@ class API {
         });
     }
 
+    /**
+     * Notify external application (if API is enabled) that the user received
+     * a transcription chunk.
+     *
+     * @param {Object} data - The event data.
+     * @returns {void}
+     */
+    notifyTranscriptionChunkReceived(data) {
+        this._sendEvent({
+            name: 'transcription-chunk-received',
+            data
+        });
+    }
+
     /**
      * Notify external application (if API is enabled) whether the used browser is supported or not.
      *

modules/API/external/external_api.js

@@ -160,6 +160,7 @@ const events = {
     'suspend-detected': 'suspendDetected',
     'tile-view-changed': 'tileViewChanged',
     'toolbar-button-clicked': 'toolbarButtonClicked',
+    'transcription-chunk-received': 'transcriptionChunkReceived',
     'whiteboard-status-changed': 'whiteboardStatusChanged'
 };
 

react/features/subtitles/middleware.ts

@@ -153,10 +153,15 @@ function _endpointMessageReceived({ dispatch, getState }: IStore, next: Function
                 newTranscriptMessage.unstable = text;
             }
 
-            dispatch(
-                updateTranscriptMessage(
-                    transcriptMessageID,
-                    newTranscriptMessage));
+            dispatch(updateTranscriptMessage(transcriptMessageID, newTranscriptMessage));
+
+            // Notify the external API too.
+            if (typeof APP !== 'undefined') {
+                APP.API.notifyTranscriptionChunkReceived({
+                    messageID: transcriptMessageID,
+                    ...newTranscriptMessage
+                });
+            }
         }
     } catch (error) {
         logger.error('Error occurred while updating transcriptions\n', error);