Update notes for version 1.18

1. Improved the skill bar usability (easier to replace skills and change the order etc.)
2. Rare items can now sometimes be found in the equipment store
3. Fixed crash relating to boarded ship being sunk and rare crash relating to NPC's ownership of flotsams
4. Fixed equipment flotsams sometimes showing up as empty.
5. Fixed two exploration locations sometimes being spawned on top of each other in the Mediterranean. Also reduced exploration location density there.
6. Small UI improvements.
7. Fixed sound volume not being applied to the rain