ci(github): test in PyPy (Python 3.10)

Author: dbohdan

.github/workflows/ci.yml

@@ -5,7 +5,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        python-version: ["3.8", "3.9", "3.10", "3.11", "3.12"]
+        python-version: ["3.8", "3.9", "3.10", "3.11", "3.12", "pypy3.10"]
     steps:
       - uses: actions/checkout@v3
       - name: Set up Python ${{ matrix.python-version }}
@@ -23,7 +23,7 @@ jobs:
     runs-on: windows-2019
     strategy:
       matrix:
-        python-version: ["3.8", "3.9", "3.10", "3.11", "3.12"]
+        python-version: ["3.8", "3.9", "3.10", "3.11", "3.12", "pypy3.10"]
     steps:
       - name: 'Disable `autocrlf` in Git'
         run: git config --global core.autocrlf false