Test both PyPy3.6 and PyPy3.7

Author: hugovk

.github/workflows/test.yml

@@ -20,7 +20,8 @@ jobs:
         ]
         include:
           # Add new helper variables to existing jobs
-          - {python-version: "pypy3", tox-python-version: "pypy3"}
+          - {python-version: "pypy-3.6", tox-python-version: "pypy3"}
+          - {python-version: "pypy-3.7", tox-python-version: "pypy3"}
           - {python-version: "3.6", tox-python-version: "py36"}
           - {python-version: "3.7", tox-python-version: "py37"}
           - {python-version: "3.8", tox-python-version: "py38"}