doc: Add godoc badge to README
doc: Add godoc badge to README

Signed-off-by: Damien Lespiau <64bd3cb94f359c1a3ce68dae5e26b40578526277@intel.com>

clearcontainers/proxy,clearcontainers/proxy,dlespiau/clearcontainers-proxy,dlespiau/proxy,dlespiau/clearcontainers-proxy,dlespiau/proxy