Add AppVeyor

Author: Arttse

appveyor.yml

@@ -0,0 +1,19 @@
+environment:
+  matrix:
+    - nodejs_version: "6"
+    - nodejs_version: "8"
+    - nodejs_version: "10"
+install:
+  - ps: Install-Product node $env:nodejs_version
+  - npm install
+test_script:
+  - node --version
+  - npm --version
+  - npm test
+build: off
+clone_depth: 1
+matrix:
+  fast_finish: true
+cache:
+  - node_modules
+  - '%APPDATA%\npm-cache'