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

Closes #16

Author: greenkeeper[bot]

package.json

@@ -29,7 +29,7 @@
     "lint-staged": "^10.0.8",
     "prettier": "^1.19.1",
     "prettier-package-json": "^2.1.0",
-    "ts-jest": "^25.2.1",
+    "ts-jest": "^26.1.0",
     "ts-node": "^8.5.4",
     "ttypescript": "^1.5.8",
     "typescript": "^3.7.2"