User Guide: Add one more examples to sonar configuration

[ckunki]

Current situation

Currently, the PTB user guide says

exclusions = "<source-directory>/version.py,<source_directory>/<directory-to-ignore>/*"

Critique

Maybe some additional sentences would be helpful?

Proposal

With the value of exclusions you can exclude files and directories of your project from Sonar analysis:

• You can use wildcards, e.g. <root>/dir/*.java or <root>/**/*.java
• Multiple exclusions can be comma-separated (see above)
• For excluding arbitrary directories and files below a specific directory, please use two asterisks, e.g. root/abc/**.

See Sonar docs for details.