Add guide to show how to set up hands poser

Add hands poser prefab

set left hand container to the left interactor, right hand container to the right interactor (this is used by the internal rules matcher)

Then expand prefab and on the `Left.BasicHandPoser` set the Target to the left avatar hand and configure any hand pose settings as required (make sure the overrides are set in the apply hand pose values dropdown otherwise they wont be applied).

Then expand the `Left.BasicHandPoser` prefab to access the finger pose overrides. The reference target doesn't need setting as it will automatically be set at runtime from the hand poser.

Each finger pose data can be set, but will only be applied iof the `apply pose values` for that option is set.

Do the same for the right hand.

Now on an interactable, you can call `ApplyPose` in the grabbed event and `RemovePose` in the ungrabbed event (dynamic event passing in the interactor)

首先找到 hands poser prefab 以及现有指南或文档的入口。记录左手和右手容器、BasicHandPoser 目标和姿势值覆盖、手指姿势覆盖，以及 ApplyPose 和 RemovePose 事件的配置方法。当新手能够按照指南配置双手和一个 interactable 时，即视为完成。

由索引模型根据 Issue 内容生成。