ci(jest): add node 15 to test matrix

Author: wopian

.github/workflows/jest.yml

@@ -10,7 +10,7 @@ jobs:
 
     strategy:
       matrix:
-        node_version: [10, 12, 14]
+        node_version: [10, 12, 14, 15]
         os: [ubuntu-latest, windows-latest, macos-latest]
 
     steps: