Update docs

[tastybento]

Update the docs based on the new feature added in these PRs:

1. Add message delivery type tags for locale strings: actionbar, title/subtitle, sound BentoBox#2910
2. Add placeholders for flag state (enabled/disabled) BentoBox#2913
3. Add Island Defaults tab to Admin Settings GUI for editing default protection flags BentoBox#2912
4. Switch blueprints from zipped .blu to plain JSON .blueprint format BentoBox#2911
5. And general documentation around the fact that MiniMessage is being used now for all locales. See Fix MiniMessage formatting: default italic on panel items and cross-nested tags in legacyToMiniMessage BentoBox#2903