add ts as dependency

Author: magicmatatjahu

package-lock.json

@@ -59,7 +59,8 @@
     "jsdoc-to-markdown": "^6.0.1",
     "markdown-toc": "^1.2.0",
     "semantic-release": "^17.3.0",
-    "ts-jest": "^26.4.4"
+    "ts-jest": "^26.4.4",
+    "typescript": "^4.2.2"
   },
   "scripts": {
     "start": "tsc --watch",