doc: create an initial README
doc: create an initial README

Provide some basics of the libseccomp project and the intent of this
repository.  I expect the README file to change as this repository
is populated.

Signed-off-by: Paul Moore <88a1d58bf22a647dce58dd91f9595600dceabba9@redhat.com>

mvo5/libseccomp-golang,seccomp/libseccomp-golang,crosbymichael/libseccomp-golang,meihuabo/libseccomp-golang,mheon/libseccomp-golang