Node version 15 added to CI (#15)

Author: Denis-Averin

.github/workflows/node.js.yml

@@ -19,7 +19,7 @@ jobs:
 
     strategy:
       matrix:
-        node-version: [10.x, 12.x, 14.x]
+        node-version: [10.x, 12.x, 14.x, 15.x]
 
     steps:
     - uses: actions/checkout@v2