Add workflow for exercise 4 with Python setup and testing steps

Author: jacobsolbergholm

.github/workflows/exercise4_workflow.yml

@@ -0,0 +1,37 @@
+name: Workflow of exercise 4
+run-name: Fourth workflow
+
+on:
+    push:
+        branches: [ main ]
+    pull_request: 
+        branches: [ main ]
+    workflow_dispatch:
+
+jobs:
+    ubuntu_job:
+        runs-on: ${{ matrix.os }}
+        strategy:
+            fail-fast: false
+            matrix:
+                python-version: [3.12, 3.13]
+                os: [ubuntu-latest, windows-latest,macos-latest]
+        steps:
+            - name: Checkout repository
+              uses: actions/checkout@v6
+
+            - name: Setup python
+              uses: actions/setup-python@v6
+              with:
+                python-version: '3.14'
+
+            - name: Install dependencies
+              run: |
+                python -m pip install --upgrade pip
+                python -m pip install -r requirements-dev.txt
+
+            - name: Check code formatting
+              run: python -m black mycode.py
+
+            - name: Run tests
+              run: python -m pytest test_mycode.py