Node expression examples (#440)

* Added example for ListExpression and sh:minus

* Added section on failure handling, added sh:exists, and semantics and example for sh:if

* Added skos prefix declaration and example for sh:distinct and sh:union

* Added sh:instancesOf and example for sh:intersection

* Example of sh:limit and sh:orderBy

* Added example for sh:offset

* Added sh:filterShape

* Examples for sh:count and sh:min

* Clean up

* Apply suggestions from code review

Co-authored-by: Ted Thibodeau Jr <[email protected]>

* PR feedback

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Co-authored-by: Ted Thibodeau Jr <[email protected]>

Author: HolgerKnublauch