docs(changelog): add #1583 fragment

Co-Authored-By: Claude Opus 5.5 <[email protected]>

changelog.d/1583-shipwrecks.md

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+- New Shipwrecks layer (Events): about 8,000 wrecks from EMODnet (CC BY 4.0)
+  and Wikidata (CC0). Each has a card with deaths, date, vessel, cause, depth,
+  position quality and a source link. Markers grow with the death toll, and
+  the same period picker as air accidents filters by year (IMBrandao, #1583).