fix(package): update mkdirp to version 1.0.4

Closes #76

Author: greenkeeper[bot]

package.json

@@ -66,7 +66,7 @@
   "dependencies": {
     "debug": "^4.1.1",
     "execa": "^2.0.3",
-    "mkdirp": "^0.5.1",
+    "mkdirp": "^1.0.4",
     "node-fetch": "^2.6.0",
     "openpgp": "^4.5.5",
     "rimraf": "^2.6.3",