Add pypy 3.8, 3.9 and 3.10 as test targets in CI.

Author: sodul

.github/workflows/ci.yml

@@ -14,7 +14,10 @@ jobs:
     strategy:
       matrix:
         os: [macos-latest, ubuntu-latest, windows-latest]
-        python-version: ["3.6", "3.7", "3.8", "3.9", "3.10", "3.11"]
+        python-version: [
+          "3.6", "3.7", "3.8", "3.9", "3.10", "3.11",
+          "pypy3.8", "pypy3.9", "pypy3.10"
+        ]
         exclude:
           - os: ubuntu-latest  # Ubuntu-latest can only install 3.7+.
             python-version: 3.6
@@ -24,7 +27,7 @@ jobs:
       - uses: actions/checkout@v3
 
       - name: Set up Python ${{ matrix.python-version }}
-        uses: actions/setup-python@v4
+        uses: actions/setup-python@v5
         with:
           python-version: ${{ matrix.python-version }}