Lootable unit corpses (UNIT_DYNFLAG_LOOTABLE) now click-through over
blocking players, matching the existing behavior for interactable NPCs
and game objects. Adds isLootable() check to the interactable NPC test
and UNIT_DYNAMIC_FLAGS descriptor offset to shared offsets.
Also adds RELEASE_NOTES.md for tracking changes between releases, and
adds a checklist item in RELEASING.md to review it before publishing.