chore(package): update ts-jest to version 26.0.0

Closes #25

Author: greenkeeper[bot]

package.json

@@ -33,7 +33,7 @@
     "rollup-plugin-node-resolve": "^3.0.0",
     "rollup-plugin-typescript2": "^0.14.0",
     "semver": "^5.4.1",
-    "ts-jest": "^23.0.0",
+    "ts-jest": "^26.0.0",
     "typescript": "^2.6.2"
   },
   "jest": {