fix(readme): update publishing guide to yarn

.yarnrc.yml

 nodeLinker: node-modules
+
+npmPublishRegistry: "https://gitlab1.ptb.de/api/v4/projects/105/packages/npm/"
+
+npmScopes:
+  d-ptb:
+    npmRegistryServer: "https://gitlab1.ptb.de/api/v4/packages/npm/"

README.md

@@ -64,25 +64,19 @@ See [the Licence](LICENSE.md) for the specific language governing permissions an
 
 ## Publishing this package
 
-Add the following to your `.npmrc`.
-```
-message="chore(release): bump version to v%s"
-# if you want to sign the tag
-sign-git-tag=true
-
-@d-ptb:registry=https://gitlab1.ptb.de/api/v4/packages/npm/
-
-# the following auth token should be a private one with write permission for the package registry
-//gitlab1.ptb.de/api/v4/projects/:_authToken=<token>
-//gitlab1.ptb.de/api/v4/packages/npm/:_authToken=<token>
-//gitlab1.ptb.de/api/v4/projects/105/packages/npm/:_authToken=<token>
+Add the following to your `.yarnrc.yml` in your **home folder**. Do not commit your token!
 
+```yml
+npmRegistries:
+  https://gitlab1.ptb.de/api/v4/projects/105/packages/npm/:
+    npmAlwaysAuth: true
+    npmAuthToken: "<token>"
 ```
 
 
 ### Publishing workflow
 
 1. Commit all changes
-2. Bump the version with `npm version [major | minor | patch | ...]`
+2. Bump the version with `yarn version [major | minor | patch | ...]`
 3. Push all commits to the remote
-4. Publish the package with `npm publish`
+4. Publish the package with `yarn npm publish`