Resolve "Update documentation on virtual env. for Alpha"

• fixed example for pytorch/torchvision in venv
• add workspace creation for venv in example
• add hint for workspaces and venv in general
• quick fix for deprecated JH section

Closes #533 (closed)

doc.zih.tu-dresden.de/docs/jobs_and_resources/alpha_centauri.md

@@ -132,7 +132,7 @@ additional Python packages and create an isolated runtime environment. We recomm
 
     We recommend to use [workspaces](../data_lifecycle/workspaces.md) for your virtual environments.
 
-??? example "Example: Creating virtual environment and installing `torchvision` package"
+??? example "Example: Creating a virtual environment and installing `torchvision` package"
 
     ```console
     marie@login.alpha$ srun --nodes=1 --cpus-per-task=1 --gres=gpu:1 --time=01:00:00 --pty bash -l