package/rapidjson: add .hash file

Similar to jquery-keyboard, it seems the rapidjson tarball on the
autobuilder is corrupt.  Fix it by adding a .hash file so it falls back to
our s.b.o mirror.

Signed-off-by: Romain Naour <romain.naour@gmail.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/rapidjson/rapidjson.hash

@@ -0,0 +1,2 @@
+# Locally calculated
+sha256 c3711ed2b3c76a5565ee9f0128bb4ec6753dbcc23450b713842df8f236d08666  rapidjson-v1.0.2.tar.gz