Update CI doc

docs/for_devs/ci.rst

 CI Pipeline
 ==================================
 
+Sassena has a CI.
+
 Building the Docker Image
 -------------------------
 Sassena uses a docker container to build the program and run the unit tests on
@@ -8,12 +10,18 @@ the CI server.
 
 Firstly, may need to create a "Personal Access Token". This can be done in the
 Gitlab settings under your personal profile settings. Once this is done, with your
-credentials, run the command::
-  docker login registry.hzdr.de
+credentials, run the command
+.. code-block::
+
+    docker login registry.hzdr.de
+
+The docker image can be build on a local machine using the command
+.. code-block::
 
-The docker image can be build on a local machine using the command::
   docker build -t registry.hzdr.de/daphne4nfdi/sassena .
 
 If you have made changes to the docker container and want to push it to the CI,
-simply update the Sassena registry using the command::
+simply update the Sassena registry using the command
+.. code-block::
+
   docker push registry.hzdr.de/daphne4nfdi/sassena