Design doc: Add intrinsic coordinate system name example (#963)

* Update design_doc.md

* update design docs around coordinate systems

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Co-authored-by: LucaMarconato <2664412+LucaMarconato@users.noreply.github.com>
Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

Author: 3 people

docs/design_doc.md

@@ -310,7 +310,7 @@ In details:
 - we don't need to specify the intrinsic coordinate systems, these are inferred from the element schema
 - each element MAY have a transformation mapping them to one or more extrinsic coordinate systems
 
-Each coordinate system
+Each extrinsic coordinate system
 
 - MUST have a name
 - MAY specify its axes