add link to GEOS C wrapper

Author: visr

README.md

@@ -4,7 +4,7 @@ LibGEOS.jl
 [![Build Status](https://ci.appveyor.com/api/projects/status/github/JuliaGeo/LibGEOS.jl?svg=true&branch=master)](https://ci.appveyor.com/project/JuliaGeo/LibGEOS-jl/branch/master)
 [![Coverage Status](https://coveralls.io/repos/github/JuliaGeo/LibGEOS.jl/badge.svg)](https://coveralls.io/github/JuliaGeo/LibGEOS.jl)
 
-LibGEOS is a package for manipulation and analysis of planar geometric objects, based on the libraries [GEOS](https://trac.osgeo.org/geos/) (the engine of PostGIS) and JTS (from which GEOS is ported).
+LibGEOS is a package for manipulation and analysis of planar geometric objects, based on the libraries [GEOS](https://trac.osgeo.org/geos/) (the engine of PostGIS) and JTS (from which GEOS is ported). This package wraps the [GEOS C API](https://geos.osgeo.org/doxygen/geos__c_8h_source.html).
 
 Among other things, it allows you to parse [Well-known Text (WKT)](https://en.wikipedia.org/wiki/Well-known_text)