Update README.md

Add section on browser compatibility.

README.md

@@ -190,4 +190,9 @@ Below are results from [perf-tests/perftest1.html](perf-tests/perftest1.html) as
 - Frustum clipping (n-gons behind the camera will result in odd behavior)
 - Depth testing (painter's sorting is used)
 
-Also, convex n-gons are not supported.
+Note also that convex n-gons are not supported.
+
+## Browser compatibility
+At the moment, versions of Chrome and Firefox released in the last year or so are supported; although, as per the performance tests above, Chrome is preferred.
+
+Safari is untested for, but newer versions of it should work.