bump version to 1.3.1-extended

package.json

@@ -1,6 +1,6 @@
 {
   "name": "opensheetmusicdisplay-private",
-  "version": "1.3.0",
+  "version": "1.3.1",
   "description": "Private OSMD mirror/audio player.",
   "main": "build/opensheetmusicdisplay.min.js",
   "typings": "build/dist/src/",

src/OpenSheetMusicDisplay/OpenSheetMusicDisplay.ts

@@ -35,7 +35,7 @@ import { DynamicsCalculator } from "../MusicalScore/ScoreIO/MusicSymbolModules/D
  * After the constructor, use load() and render() to load and render a MusicXML file.
  */
 export class OpenSheetMusicDisplay {
-    private version: string = "1.3.0-audio-extended"; // getter: this.Version
+    private version: string = "1.3.1-audio-extended"; // getter: this.Version
     // at release, bump version and change to -release, afterwards to -dev again
 
     /**