ci(appveyor.yml): updates appveyor to use current versions of node

* Bump autoprefixer version

Author: jlengrand

CONTRIBUTING.md

@@ -24,7 +24,7 @@ When you have a local copy of the project up and running, create a new branch wi
 git checkout -b patch-1
 ```
 
-Create Elm App uses [Commitizen](https://github.com/commitizen/cz-cli) and [semantic-release](https://github.com/semantic-release/semantic-release) for release automatization.
+Create Elm App uses [Commitizen](https://github.com/commitizen/cz-cli) and [semantic-release](https://github.com/semantic-release/semantic-release) for release automation.
 
 Commit changes by running `npm run cz`
 

appveyor.yml

@@ -7,8 +7,8 @@ platform:
 environment:
   matrix:
   # node.js
-    - nodejs_version: "8"
     - nodejs_version: "12"
+    - nodejs_version: "14"
 
 matrix:
   fast_finish: true