prepare for automatic build

.gitlab-ci.yml

 stages:
 - test
+- build
 - release
 
 
@@ -18,6 +19,26 @@ test:doctest:
   script:
   - python -m doctest -v src/dokos/dokos.py
 
+build:
+  stage: build
+  image: python:3.10
+  rules:
+    - if: $CI_COMMIT_TAG
+  artifacts:
+    paths:
+      - pyproject.toml
+      - dist
+  before_script:
+    # install envsubst
+    # python:3.10 is based on debian bullseye
+    - apt-get install -y gettext-base
+    - apt-get install -y python3-venv 
+    - python3 -m pip install --upgrade build
+  script:
+    # create the new docker-compose
+    - envsubst < pyproject.tmpl > pyproject.toml
+    - python3 -m build
+
 release:
   stage: release
   image: registry.gitlab.com/gitlab-org/release-cli:latest