chore: requires at least Node 10.13 (#63)

* chore: requires at least Node 10.13

- 'recursive' option in fs.mkdir() & fs.mkdirSync() is introduced in Node 10.12

* ci(appveyor): add Node 14

appveyor.yml

@@ -8,6 +8,7 @@ environment:
     - nodejs_version: "10"
     - nodejs_version: "12"
     - nodejs_version: "13"
+    - nodejs_version: "14"
 
 matrix:
   fast_finish: true

package.json

@@ -43,6 +43,6 @@
     "nyc": "^15.0.0"
   },
   "engines": {
-    "node": ">=10"
+    "node": ">=10.13.0"
   }
 }