Add continuous integration pipeline

Added basic continuous integration tests to run on any push:
On main branch, the python program is built.
On tagged commit, a gitea release is created.

Fixed first detected build pipeline issues:
Fixing mypy library stubs missing for some imported libraries.
Fixed two small typing errors for Repetitions.

The steps run on basic python containers, onto which the ci steps simply
install poetry.
This takes a little more processing time during pipeline running (~16s
per step),
but also gives a lot of flexibility in container usage.

Added script which assists in creating an automatic release by
extracting the current version and newest changes from the semantic
changelog.
This is then used in the gitea release preparation as title and
content of the release message.
The files built in the dist directory by poetry will be attached.

.woodpecker.yml

@@ -57,17 +57,7 @@ pipeline:
       title: NEWEST_VERSION.md
       note: NEWEST_CHANGES.md
     when:
-      event: tag
+      branch: main
-      tag: v*
-
-  pypi_release:
-    image: python
-    commands:
-      - pip install poetry
-      - poetry install
-      - echo "----------------- publishing to pypi ------------------"
-      - poetry publish --username "$PYPI_USERNAME" --password "$PYPI_PASSWORD"
-    when:
       event: tag
       tag: v*