Feature/mad 91 gitlab pipeline

Gitlab pipeline definition for build, test + deploy. README updated with relevant information + description of steps for running the same jobs locally. Feel free to edit the README as you see fit.

.gitlab-ci.yml

+default:
+    image: python:3.10
+
+stages:
+    - build
+    - test
+    - deploy
+
+before_script:
+    - python -V
+    - python -m venv venv
+    - . venv/bin/activate 
+    - pip install --upgrade pip
+    - pip install -e .
+
+build:
+    stage: build
+    tags:
+        - vips-runner
+    script: 
+        - pip install build
+        - python -m build
+    artifacts:
+        paths:
+            - dist/*.whl
+        expire_in: 2 days
+
+test:
+    stage: test
+    tags:
+        - vips-runner
+    script:
+        - pip install pytest
+        - pytest
+
+deploy:
+    stage: deploy
+    only: 
+        - main
+    tags:
+        - vips-runner
+    script:
+        - pip install twine
+        - TWINE_PASSWORD=${CI_JOB_TOKEN} TWINE_USERNAME=gitlab-ci-token python -m twine upload --repository-url https://gitlab.nibio.no/api/v4/projects/401/packages/pypi dist/* --verbose