updated README to include build steps
updated README to include build steps

Added the steps to build usm-client to
README.md

Signed-off-by: Kanagaraj M <a744b691cd98174fb19a473a8cf78b810491e452@redhat.com>

kmkanagaraj/usm-client,kamleshverma1/usm-client,kamleshverma1/usm-client,karnan4ever/usm-client,karnan4ever/usm-client,kmkanagaraj/usm-client