Merge pull request #263 from Fienne/update-content

feat: add cwl runner source

Author: swzCuroverse

src/introduction/prerequisites.md

@@ -57,6 +57,11 @@ $ source venv/bin/activate
 $ (venv) pip install cwltool
 ```
 
+```{note}
+You can find the `cwl-runner` source code [here](https://github.com/common-workflow-language/cwltool/tree/main/cwlref-runner).  
+Visit the `cwltool` [documentation](https://github.com/common-workflow-language/cwltool#install)
+for other ways to install `cwltool` with `apt` and `conda`.
+```
 Let's use a simple CWl tool description `true.cwl` with `cwltool`.
 
 ```{literalinclude} /_includes/cwl/true.cwl