docs: documentation updates

Author: missinglink

README.md

@@ -34,14 +34,30 @@ const { s2 } = require('s2js')
 </script>
 ```
 
-### Typescript Support
-
-The library is written in Typescript and exports type definitions.
+### Features
+
+s2js is a full-featured JavaScript/TypeScript port of Google's S2 Geometry library. It supports:
+
+| Feature                          | Supported? | Notes |
+|----------------------------------|:---------:|:------|
+| **CellId, Cell**          | ✅        | Encoding, decoding, neighbors |
+| **Point, LatLng**          | ✅        | Spherical & Planar projections |
+| **Loop, Polygon**                    | ✅        | Polygons, potentially with holes |
+| **Polyline**                   | ✅        | Represents linear paths |
+| **RegionCoverer**                | ✅        | Cover regions (loops, polys) with S2 cells |
+| **GeoJSON <> S2 conversions**    | ✅        | Supports all GeoJSON geometry types |
+| **Polygon contains/intersects**  | ✅        | Point-in-polygon & shape intersection |
+| **Union, Intersection, Difference** | ✅    | Basic boolean polygon operations |
+| **BigInt cell/token conversion** | ✅        | Handles full 64-bit cell IDs |
 
 ### Feature Completeness
 
 The library is essentially feature compatible with the Golang library: https://github.com/golang/geo
 
+### Typescript Support
+
+The library is written in Typescript and exports type definitions.
+
 ### GeoJSON support
 
 The supplementary `geojson` module provides convenience functions for working with GeoJSON data in S2: