ci: add comments to the GitHub action code

.github/workflows/test_python_package.yml

@@ -2,7 +2,7 @@
 name: Test Python Package
 
 on:
-  # Runs on pull requests targeting the default branch
+  # Runs on pull requests targeting the default branches
   pull_request:
     types: [opened, edited, reopened, synchronize]
     branches: ["master", "develop"]
@@ -20,18 +20,24 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
+        # Run on all the supported Python versions
         python-version: ["3.7", "3.8", "3.9", "3.10", "3.11", "3.12"]
+        # Run on all the supported platforms
         os: [ubuntu-latest, windows-latest, macos-latest]
 
     steps:
+    # Checkout the repository
     - name: Checkout
       uses: actions/checkout@v4
+    # Set up the correct version of Python
     - name: Set up Python ${{ matrix.python-version }} on ${{ matrix.os }}
       uses: actions/setup-python@v4
       with:
         python-version: ${{ matrix.python-version }}
+    # Install the build dependencies
     - name: Install dependencies
       run: python -m pip install --upgrade pip wheel build setuptools
+    # Install the crappy Python module
     - name: Install Crappy
       run: python -m pip install .
     - name: Import Crappy