Make withCtx easier to use in projects

[dadajam4]

Feature Request

1. Allow withCtx to accept type parameters

Currently, withCtx does not accept type parameters and always returns a Function type. This causes type errors when used with slot functions that have specific typings in consuming components.
It would be helpful if withCtx accepted a generic type and returned the same function type:

export function withCtx<Fn extends Function>(
  fn: Fn,
  ctx: ComponentInternalInstance | null = currentRenderingInstance,
  isNonScopedSlot?: boolean,
): Fn

2. Add documentation for withCtx usage

When building a component library with JSX, we encountered a warning in production caused by not wrapping a slot function with withCtx:

[Vue warn]: Slot "default" invoked outside of the render function: this will not track dependencies used in the slot. Invoke the slot function inside the render function instead.

It took significant time to trace this back to the missing withCtx wrapper. Adding documentation or usage notes—especially for JSX or render function contexts—would help developers avoid this issue.