update isort workflow

.github/workflows/run_isort.yml

@@ -1,15 +1,20 @@
 name: "Import checker"
 
-on: [push]
+on:
+  - push
 
 jobs:
   build:
+
     runs-on: ubuntu-latest
+
     steps:
     - uses: actions/checkout@v2
     - name: Set up Python 3.9
       uses: actions/setup-python@v2
       with:
         python-version: 3.9
+    - name: Install isort
+      run: pip install isort
     - name: Run isort
       run: isort . --settings-path .isort.cfg