Add node 15

Michal Vlasák · Michal Vlasák · commit a247142a0646 · 2020-11-23T14:32:57.000+01:00
diff --git a/.travis.yml b/.travis.yml
@@ -5,6 +5,7 @@ node_js:
 - '12'
 - '13'
 - '14'
+- '15'
 script:
 - npm run lint
 - npm run build
