docs: update readme

Signed-off-by: yoshiri <[email protected]>

sensing/pointcloud_preprocessor/docs/vector-map-inside-area-filter.md

@@ -10,6 +10,7 @@ The `vector_map_inside_area_filter` is a node that removes points inside the vec
 - Extract the vector map area that intersects with the bounding box of input points to reduce the calculation cost
 - Create the 2D polygon from the extracted vector map area
 - Remove input points inside the polygon
+- If the z value is used for filtering, remove points that are below the z threshold
 
 ![vector_map_inside_area_filter_figure](./image/vector_map_inside_area_filter_overview.svg)
 
@@ -35,5 +36,7 @@ This implementation inherits `pointcloud_preprocessor::Filter` class, so please
 | Name           | Type   | Description                 |
 | -------------- | ------ | --------------------------- |
 | `polygon_type` | string | polygon type to be filtered |
+| `use_z`        | bool   | use z value for filtering   |
+| `z_threshold`  | float  | z threshold for filtering   |
 
 ## Assumptions / Known limits