Test all python versions in CI

Followed instructions here: https://docs.github.com/en/actions/automating-builds-and-tests/building-and-testing-python#using-the-python-starter-workflow

.github/workflows/python-build-test.yml

@@ -14,6 +14,10 @@ jobs:
   build:
 
     runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        python-version: ["3.8", "3.9", "3.10"]
+      fail-fast: false
 
     steps:
     - name: Check out from Git
@@ -22,10 +26,10 @@ jobs:
       run: |
         git fetch --prune --unshallow
         git fetch --depth=1 origin +refs/tags/*:refs/tags/*
-    - name: Set up Python 3.10
-      uses: actions/setup-python@v3
+    - name: Set up Python ${{ matrix.python-version }}
+      uses: actions/setup-python@v4
       with:
-        python-version: "3.10"
+        python-version: ${{ matrix.python-version }}
     - name: Install dependencies
       run: |
         python -m pip install --upgrade pip