Renable CI/CD testing on PyPy for all platforms.

PyPy's Windows unicode handling transpired to be significantly different
enough that a PyPy+Windows specific test failure slipped in (#552).

Author: bwoodsend

.github/workflows/test.yml

@@ -16,6 +16,8 @@ jobs:
         include:
           - { python-version: "3.10", os: windows-latest }
           - { python-version: "3.10", os: macos-latest }
+          - { python-version: "pypy-3.8", os: windows-latest }
+          - { python-version: "pypy-3.8", os: macos-latest }
 
     steps:
       - uses: actions/checkout@v2