docs: add camera, audio and voice chat guides

[Kheartz]

First of three stacked PRs (camera and sound, then mounts and races, then appearance). This one is based on main.

Adds a Camera and sound section (sidebar orders 70–79), written for 1.8.2 and checked against the v1.8.2 Mod source and its Framework pin:

• Camera: capture/activate/restore, moves, paths and orbits, lens, fades, shakes.
  • The custom camera is shared by every resource on a client and isn't handed back when a resource stops, so the guide restores it in resourceStop and only when Camera.active.
  • Look-at stays armed after an orbit, stop and restore, so the samples call clearLookAt() before each new shot.
  • An orbit jumps onto its circle from wherever the camera is, so the sample activates on the circle first.
• Audio: the server's four ways to play a sound and who hears each, held sounds and stop events, client sounds, soundbanks and music.
  • Server sounds ignore virtual worlds and reach only players in range when they start. Music, states and banks reach only players connected at the time.
  • The guide shows filtering by world with client playback.
• Voice chat: who hears whom (range, virtual worlds, mutes, streaming distance, six talkers at most), tiers and ranges, mutes and deafens, talking events, and each player's client settings.
  • Ranges are centimetres: 800 / 2500 / 6000 for whisper, normal and shout.
  • Voice.setRange(0) sets 25 cm rather than the default, so the guide says to pass 2500 instead.

Also in this PR:

• The overview's client camera example orbited the camera's own position and restored in the same tick. It now orbits the player and restores on a second key press.
• check_samples.mjs lets a JavaScript sample pass an untyped event argument (unknown) on to a function, as it already lets it read members of one. In 1.8.2, events outside the small typed map, such as playerDownedEnd, hand JS samples unknown arguments.

Checks: check_samples (101 samples, 1.8.2 contract), docs.mjs build, check_links and git diff --check all pass.