feat: add documentation for automatic publishing

Since the workflow is already implemented and working but not
concisely documented and known by everyone who has the
appropriate rights we need a documentation for it so that the
aforementioned persons are able to create new NPM packages
by correctly making use of the GitLab CI job.

Fixes #23

project-docs/workflow/PUBLISHING.md

@@ -0,0 +1,37 @@
+# Publishing
+
+## NPM
+
+All projects that use the [OpenStApps configuration](https://gitlab.com/openstapps/configuration) and implement the automatic publishing via GitLab CI can simply be published to the NPM registry by using the appropriate job. It uses the `NPM_AUTH_TOKEN`  that is a [protected variable](https://gitlab.com/groups/openstapps/-/settings/ci_cd) of the OpenStApps group. To trigger this job, a new tag has to be created (on the master branch):
+
+### Use current [master branch](BRANCHING.md):
+
+```shell
+git checkout master
+git pull
+```
+
+### Update [version](VERSIONING.md)
+
+```shell
+npm version (major|minor|patch)
+```
+   
+After these steps there should 2 new commits:
+
+* A version commit
+* A changelog commit
+
+Also a new git tag should be created.
+
+**CAUTION: Make sure that everything was successful, before running the next command, that pushes commits to GitLab!**
+
+### Pushing commits and version tag created in previous step
+
+To push the previously created commits and version tag you can use the following convenience script:
+
+```shell
+npm run push
+```
+
+After you've pushed the commits and tags a pipeline will be started for the tag that includes a job that will automatically publish a new package to the NPM registry.