ci: test in Node 13, stop testing in Node 8

Author: gr2m

.github/workflows/test.yml

@@ -11,7 +11,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        node_version: [8, 10, 12]
+        node_version: [10, 12, 13]
 
     steps:
       - uses: actions/checkout@v2