chore: update appveyor to node 12 from node 10 to hopefully fix builds

.appveyor.yml

@@ -3,7 +3,8 @@ environment:
   timeout: 10000
   matrix:
     # - nodejs_version: "8" 
-    - nodejs_version: "10"
+    # - nodejs_version: "10"
+    - nodejs_version: "12"
 platform:
   # - x86
   - x64