Test a range of pymodbus versions (#42)

* Test a range of pymodbus versions

* Install pymodbus first to avoid re-install

* Pymodbus 3 doesn't work on Python3.7

.github/workflows/python-package.yml

@@ -17,6 +17,18 @@ jobs:
       fail-fast: false
       matrix:
         python-version: ["3.7", "3.8", "3.9", "3.10", "3.11"]
+        pymodbus-version: ["2.5.3", "3.0.2", "3.1.3", "3.2.2"]
+        exclude:
+        - python-version: "3.10"
+          pymodbus-version: "2.5.3"
+        - python-version: "3.11"
+          pymodbus-version: "2.5.3"
+        - python-version: "3.7"
+          pymodbus-version: "3.0.2"
+        - python-version: "3.7"
+          pymodbus-version: "3.1.3"
+        - python-version: "3.7"
+          pymodbus-version: "3.2.2"
 
     steps:
     - uses: actions/checkout@v3
@@ -27,6 +39,7 @@ jobs:
     - name: Install dependencies
       run: |
         python -m pip install --upgrade pip
+        python -m pip install 'pymodbus==${{ matrix.pymodbus-version }}'
         python -m pip install '.[test]'
     - name: Lint with ruff
       run: |