fix typo in README

Author: yeesian

README.md

@@ -1,6 +1,6 @@
 LibGEOS.jl
 ==========
-LibGEOS is a GPL-licensed 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 LGPL-licensed 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).
 
 Among other things, it allows you to parse [Well-known Text (WKT)](https://en.wikipedia.org/wiki/Well-known_text)