chore: use node 15 in ci

Author: vasco-santos

.github/workflows/main.yml

@@ -27,7 +27,7 @@ jobs:
     strategy:
       matrix:
         os: [windows-latest, ubuntu-latest, macos-latest]
-        node: [14]
+        node: [14, 15]
       fail-fast: true
     steps:
       - uses: actions/checkout@v2