Add note about tileserver-gl-light to docs

docs/installation.rst

@@ -9,11 +9,16 @@ When running docker image, no special installation is needed -- the docker will
 
 Just run ``docker run -it -v $(pwd):/data -p 8080:80 klokantech/tileserver-gl``.
 
-NPM
+npm
 ===
 
 Just run ``npm install -g tileserver-gl``.
 
+``tileserver-gl-light`` on npm
+==============================
+
+Alternatively, you can use ``tileserver-gl-light`` package instead, which is pure javascript (does not have any native dependencies) and can run anywhere, but does not contain rasterization features.
+
 
 From source
 ===========