Mention the R wrapper in the README file.

Fixes #105.

Change-Id: I86ea45ddb1db0dd9f74f193974cfd5322121d9be
Reviewed-on: https://code-review.googlesource.com/6730
Reviewed-by: Paul Wankadia <[email protected]>
diff --git a/README b/README
index 3686a86..5d8d2ae 100644
--- a/README
+++ b/README
@@ -34,4 +34,5 @@
 An OCaml wrapper is at https://github.com/janestreet/re2/ and on OPAM.
 A Perl wrapper is at https://github.com/dgl/re-engine-RE2/ and on CPAN.
 A Python wrapper is at https://github.com/facebook/pyre2/.
+An R wrapper is at https://github.com/qinwf/re2r/.
 A Ruby wrapper is at https://github.com/mudge/re2/.