docs: add appearance guide

[Kheartz]

Third of three stacked PRs. #12 and #13 have merged, so this is now based on main and its diff is this page alone.

Adds Appearance to the Players section (order 33), written for 1.8.2 and checked against the v1.8.2 Mod source:

• The look: getLook() fields, playerAppearanceChanged(player, look, revision), appearanceRevision.
• Saving and restoring looks:
  • Nothing is saved and players join as the default character, so the sample restores on loadingFinished.
  • It doesn't save until the restore is done, because the first look a joining player sends is the default.
  • It skips looks with no presets.
  • It notes that setLook replaces the whole look; that the callback runs after the rebuild (20 s timeout); and that it throws INVALID_APPEARANCE without a callback.
  • A look's gear and house don't dress the player's own body. Clothes come from the inventory and the house from player.house.
• The character creator: Creator.open() and the creatorConfirmed / creatorCancelled client events. A disguise pauses look publication, so take it off first. A short note covers script sessions, CreatorPreview and Portrait.
• Clothes, house and gender, size, disguises, props:
  • Gear covers player.gear.apply, inventory.give(..., { equipped: true }) and playerGearChanged.
  • player.house changes robes and crest. player.gender only sets the dormitory.
  • setScale has full and visual modes.
  • setTransmog should be checked with Character.isAllowed, isn't part of the look, and setLook removes it.
  • equipProp drops a prop sent before the player has a body.
  • All of these last for the visit only.

Also fixes the events table, which named playerAppearanceChanged's second argument blob; it is the parsed look.

Checks: check_samples (116 samples, 1.8.2 contract), docs.mjs build, check_links and git diff --check all pass.