builtin/settingtypes.txt: Update zoom description.

[ghost]

No description provided.

[paramat]

Nice i forgot to update this, but it needs to be something like:
This requires the player object property 'can_zoom' to be true.

[SmallJoker]

Another suggestion:
Instead of mixing lua_api and the settings in this case, how about simply using Field of view while zooming in degrees. Requires to be allowed by server-sided mods. ?
Most players aren't modders, so this will be easier to understand for them.
More important: Where's the can_zoom table key/value documented @paramat ?

[paramat]

Yes i'm fine with Krock's suggestion.
I forgot to document it in lua_api.txt, sorry, will fix.