Add CI/CD pipeline configuration

.gitlab-ci.yml

+stages:
+  - build
+  - test
+  - deploy
+
+build:
+  stage: build
+  script:
+    - echo "Building the project..."
+    - python train_model.py
+
+test:
+  stage: test
+  script:
+    - echo "Testing the project..."
+    - jupyter nbconvert --execute --to notebook --inplace test_flask_app_task3.ipynb
+    - jupyter nbconvert --execute --to notebook --inplace test_flask_app_task4.ipynb
+
+deploy:
+  stage: deploy
+  script:
+    - echo "Deploying the project..."
+    - # Add your deployment steps here
+