chore(package): update ts-jest to version 26.1.0

Closes #3

Author: greenkeeper[bot]

package.json

@@ -32,7 +32,7 @@
     "@types/jest": "^24.0.0",
     "jest": "^24.1.0",
     "np": "^4.0.2",
-    "ts-jest": "^23.1.3",
+    "ts-jest": "^26.1.0",
     "typescript": "^3.0.1"
   },
   "publishConfig": {