normative refs: add IFC2x3 CV2.0 to doc2

[ReesePlews]

this normative ref is used in doc1, it needs to be added to doc2 (for a table source reference), for now we will keep as a normative ref. if there are other references in doc2 it could be moved to the bibliography;

IFC2x3 CV2.0, buildingSMART International. IFC 2×3 Coordination View 2.0. ⼊⼿先: https://standards.buildingsmart.org/IFC/RELEASE/IFC2x3/FINAL/HTML/