Release version 2.4.0

Author: c-w

package.json

@@ -51,7 +51,7 @@
     "type": "git",
     "url": "https://github.com/c-w/mathquill4quill"
   },
-  "version": "2.3.0",
+  "version": "2.4.0",
   "main": "mathquill4quill.js",
   "files": [
     "build/mathquill4quill.min.css",