Add ArangoDB 3.8 to test matrix

Author: pluma

.github/workflows/tests.yml

@@ -13,7 +13,7 @@ jobs:
       fail-fast: false
       matrix:
         node-version: [10, 12, 14, 16]
-        arangodb-version: [3.6, 3.7]
+        arangodb-version: [3.6, 3.7, 3.8]
 
     container:
       image: node:${{ matrix.node-version }}