run CI on more julia versions (#22)

Author: KristofferC

.github/workflows/ci.yml

@@ -22,7 +22,8 @@ jobs:
       fail-fast: false
       matrix:
         version:
-          # - '1.6'
+          - '1.6'
+          - '1.7'
           - 'nightly'
         os:
           - ubuntu-latest