Update .gitlab-ci.yml file

.gitlab-ci.yml

+stages:          # List of stages for jobs, and their order of execution
+  - test
+  - build
+  - deploy
+
+flake8:
+    stage: test
+    image: python:3.10-alpine
+    before_script:
+        - pip install flake8
+    script:
+        - flake8 . -v