Add p5 wiki page for eCTD v4.0 (vs. eCTD v3.2)

[robertdevine]

eCTD 4.0 significantly shifts from a document-centric to a data-driven approach, featuring a single XML file and unique document identifiers for better data reuse, unlike eCTD 3.2. Post a high-level wiki narrative of the FDA final guidance document describing the harmonized changes and impacts to provide historical context for readers. [May be an appropriate task for use of generative Ai with LLM/MLLM.]