Added install step to deploy stage

Author: s1hofmann

.travis.yml

@@ -59,6 +59,7 @@ jobs:
       osx_image: xcode11
       language: node_js
       node_js: lts/erbium
+      install: npm ci
       script: true
       before_deploy:
         - echo "//registry.npmjs.org/:_authToken=\${NPM_TOKEN}" >> $HOME/.npmrc 2> /dev/null