Move container documentation to docs/.

docs/HowTos.md

 
 - [Event displays HowTo](eventdisplay/HowTo.md)
 - [Histogram servers HowTo](histservs/HowTo.md)
+- [Online Container HowTo](online/container/HowTo.md)

algo/containers/README → docs/online/container/HowTo.md

+# Online Container
+
+This document provides an overview over the containers currently used for CBM online operations, how to build them and test the reconstruction container.
+
 ## Build container
 
 ### Login
@@ -30,19 +34,26 @@ Building the online code and creating a new image, happens inside a container vi
 To build new cbm_online-images locally, you first have to create a new build-image:
 ```
 cd <CbmRoot>
-./algo/containers/cbm_online/make_build_image.sh <gitlab_user> <gitlab_password>
+./algo/containers/cbm_online/make_build_image.sh <gitlab_user> <gitlab_password> <tag>
 ```
 **This will store your password in plain text in the container. Make sure to delete after you're done.**
 
+The image tag is optional. If no tag is provided, defaults to `<gitlab_user>-debug`.
+
 Then run the new container, to build a new cbm_online-image:
 ```
 docker run -it --rm cbm_online_builder
 ```
 
-This will push a new container image `cbm_online:<gitlab_user>-debug` to the CbmRoot registry.
+This will push a new container image `cbm_online:<tag>` to the CbmRoot registry.
+
+Pull the new image first with:
+```
+docker pull hub.cbm.gsi.de/computing/cbmroot/cbm_online:<gitlab_user>-debug
+```
 
 You can use `test_run.sh` or `test_run_gpu.sh` scripts to test the image locally.
-Make sure to pull the new image first with: `docker pull hub.cbm.gsi.de/computing/cbmroot/cbm_online:<gitlab_user>-debug`
+
 
 ## Test on virgo
 
@@ -63,4 +74,6 @@ MR `N`.
 
 Run the container on the virgo debug partition with GPUs:
 
-```srun --constraint=mi50 -p debug apptainer exec cbm_online.sif cbmreco -p /lustre/cbm/online/params -i /lustre/cbm/online/data/2391_node8_0_0000.tsa -d hip0 -n1```
+```
+srun --constraint=mi50 -p debug apptainer exec cbm_online.sif cbmreco -p /lustre/cbm/online/params -i /lustre/cbm/online/data/2391_node8_0_0000.tsa -d hip0 -n1
+```