chore(ci): add linting to CI

Author: Steven Vancoillie

.travis.yml

@@ -21,6 +21,7 @@ env:
 before_install:
   - docker run -d --rm -p 8554:8554 steabert/gst-rtsp-launch
 script:
+  - yarn lint
   - yarn test
   - yarn build
   - node rtsp-ws-server/tcp-ws-proxy.js >& tcp-ws-proxy.log &
@@ -39,9 +40,9 @@ deploy:
       repo: AxisCommunications/media-stream-library-js
       node: '12'
   - provider: npm
-    email: "$NPM_EMAIL"
-    tag: "$NPM_TAG"
-    api_key: "$NPM_TOKEN"
+    email: '$NPM_EMAIL'
+    tag: '$NPM_TAG'
+    api_key: '$NPM_TOKEN'
     skip_cleanup: true
     on:
       tags: true