add previous versions of node to the test matrix

Author: mattberther

.github/workflows/unit-tests.yml

@@ -12,7 +12,7 @@ jobs:
 
     strategy:
       matrix:
-        node-version: [12.x, 14.x, 16.x, 17.x]
+        node-version: [8.x, 10.x, 12.x, 14.x, 16.x, 17.x]
 
     steps:
       - uses: actions/checkout@v2