Add Python 3.10 to GitHub Actions workflows

Beta releases of Python 3.10 were installed with `"3.10.0-beta - 3.10"`.
Python 3.10 is now stable, so beta versions are no longer needed.

.github/workflows/builds.yml

@@ -18,7 +18,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        python-version: [3.8, 3.9]
+        python-version: ["3.8", "3.9", "3.10"]
     steps:
       - uses: actions/checkout@v2
       - uses: actions/setup-python@v2
@@ -64,7 +64,7 @@ jobs:
         with:
           fail_ci_if_error: true
           flags: unit
-      - name: Build Python package with latest Python version and publish to PyPI
+      - name: Build Python package with latest stable Python version and publish to PyPI
         if: startsWith(github.ref, 'refs/tags/') && matrix.python-version == 3.9
         run: poetry publish --build -u __token__ -p ${{ secrets.PYPI_TOKEN }}
   docker:
@@ -73,7 +73,7 @@ jobs:
     strategy:
       matrix:
         linux-version: ["", "alpine", "slim"]
-        python-version: [3.8, 3.9]
+        python-version: [3.8, 3.9, 3.10]
     steps:
       - uses: actions/checkout@v2
       - uses: actions/setup-python@v2

.github/workflows/hooks.yml

@@ -16,7 +16,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        python-version: [3.8, 3.9]
+        python-version: ["3.8", "3.9", "3.10"]
     steps:
       - uses: actions/checkout@v2
       - uses: actions/setup-python@v2

.github/workflows/tests.yml

@@ -20,7 +20,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        python-version: [3.8, 3.9]
+        python-version: ["3.8", "3.9", "3.10"]
     steps:
       - uses: actions/checkout@v2
       - uses: actions/setup-python@v2