Add node v12 to appveyor as well

bjornstar · bjornstar · commit 09dde58c57dc · 2019-04-25T14:07:46.000+09:00
diff --git a/appveyor.yml b/appveyor.yml
@@ -21,6 +21,7 @@ environment:
     - nodejs_version: "9.11"
     - nodejs_version: "10.15"
     - nodejs_version: "11.14"
+    - nodejs_version: "12"
 
 services:
   - mysql
