Added ruff to github CI

Author: Lukas Molleman

.github/workflows/runtests.yml

@@ -23,7 +23,10 @@ jobs:
           python-version: '3.11'
       - run: python -m pip install --upgrade pip
 
-      - run: pip install flake8
+      - run: pip install flake8 ruff
 
-      - name: Run flake8 on the sympy package
+      - name: Run flake8 on the sympy benchmark package
         run: flake8 benchmarks slow_benchmarks
+
+      - name: Run Ruff on the sympy benchmark package
+        run: ruff check .