chore(package): update vexflow to 1.2.88

tested with all samples, no breaking changes seen

package.json

@@ -52,7 +52,7 @@
     "jszip": "^3.0.0",
     "loglevel": "^1.5.0",
     "typescript-collections": "^1.1.2",
-    "vexflow": "^1.2.87"
+    "vexflow": "^1.2.88"
   },
   "devDependencies": {
     "@types/chai": "^4.0.3",