[licenses] Add path to LICENSE file in README.fuchsia.

This makes it easier for license checking tools to find
the correct license file.

More info: http://shortn/_S8Rzw4fSCw

Change-Id: I66762e2afa469974fc1e74a53bfbca7e09fd66b7
Reviewed-on: https://fuchsia-review.googlesource.com/c/third_party/rapidjson/+/767092
Reviewed-by: Bruno Dal Bo <brunodalbo@google.com>
Commit-Queue: Jerry Belton <jcecil@google.com>

README.fuchsia

diff --git a/README.fuchsia b/README.fuchsia
index b275c52..b7ac59a 100644
--- a/README.fuchsia
+++ b/README.fuchsia
@@ -1,5 +1,7 @@
 Name: rapidjson
 URL: https://github.com/Tencent/rapidjson/archive/v1.1.0.tar.gz
+License File: license.txt
+License File: LICENSE
 Description:
 
 A fast JSON parser/generator for C++ with both SAX/DOM style API.