How to add external library for program like libjson-rpc-cpp

[chenzhijun45]

According to the documentation here(https://usoc21.unikraft.org/docs/sessions/05-contributing-to-unikraft/#warm-up), I still don't know how to add external dependencies, such as libjson-rpc-cpp(https://github.com/cinemast/libjson-rpc-cpp), how can I set up Makefile.uk and Config.uk, please?