test: Add isort check to CI/CD.

.gitea/workflows/tests.yaml

@@ -23,7 +23,7 @@ jobs:
       - run: pip install mypy
       - run: mypy org_rw --check-untyped-defs
 
-  formatting:
+  style-formatting:
     runs-on: ubuntu-latest
     steps:
       - name: Check out repository code
@@ -33,6 +33,16 @@ jobs:
       - run: pip install black
       - run: black --check .
 
+  style-sorted-imports:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Check out repository code
+        uses: actions/checkout@v3
+      - run: apt-get update && apt-get install -y python3-pip
+      - run: pip install -e .
+      - run: pip install isort
+      - run: isort --check .
+
   stability-extra-test:
     runs-on: ubuntu-latest
     steps: