travis: add node 14 to the test environments list (#658)

Co-authored-by: Pablo Palacios <[email protected]>

.travis.yml

@@ -3,6 +3,7 @@ language: node_js
 node_js:
   - 10
   - 12
+  - 14
 before_install:
   - |
     if ! git diff --name-only $TRAVIS_COMMIT_RANGE | grep -qvE '(\.md$)|(^(docs|examples))/'