Docu update: already refer to containers in 'Getting Started' section

doc/container/index.rst

@@ -13,6 +13,7 @@
 ..  See the License for the specific language governing permissions and
 ..  limitations under the License.
 
+.. _container:
 
 |project| and Containers
 ========================

doc/gettingstarted.rst

@@ -19,7 +19,7 @@ Getting Started
 
 Get and Run |project|
 --------------------------------------------------------------------------------
-First steps to get |project| up and running:
+Either utilize :ref:`containers <container>` or start from source code:
 
 #. Fetch the source code from https://git.scicore.unibas.ch/schwede/ProMod3.git.
    Or directly pull it with git: