add a sentence about singcvmfs

Author: bedroge

docs/05_advanced.md

@@ -342,6 +342,9 @@ An advantage of this method is that the cache can be shared by several processes
 !!! note
 This currently only works on RHEL 6/7/8 and its derivatives, and SUSE 15 and its derivatives.
 
+Besides `cvmfsexec` itself, the project also offers a `singcvmfs` script that can be used to easily launch Singularity containers with a CernVM-FS mount;
+this also uses the aforementiond `--fusemount` flag.
+More information about this script can be found on the [README page of the GitHub repository](https://github.com/cvmfs/cvmfsexec#singcvmfs-command).
 
 ## 5.6 Using a configuration repository