Update README.md

Author: kojix2

README.md

@@ -1,11 +1,13 @@
 # ruby-hdf5
 
+[![test](https://github.com/kojix2/c2ffi4rb/actions/workflows/ci.yml/badge.svg)](https://github.com/kojix2/c2ffi4rb/actions/workflows/ci.yml)
+
 experimental Ruby bindings for the HDF5 library
 
 ## Development
 
-- c2ffi
-- c2ffi4rb
+- [c2ffi](https://github.com/rpav/c2ffi)
+- [c2ffi4rb](https://github.com/kojix2/c2ffi4rb)
 
 ## License