Updated README to include problem.json short spec
Updated README to include problem.json short spec

cganas/picoCTF-shell-manager,picoCTF/picoCTF-shell-manager,RitwikGupta/picoCTF-shell-manager,RitwikGupta/picoCTF-shell-manager,RitwikGupta/picoCTF-shell-manager,cganas/picoCTF-shell-manager,picoCTF/picoCTF-shell-manager,cganas/picoCTF-shell-manager,cganas/picoCTF-shell-manager,picoCTF/picoCTF-shell-manager,picoCTF/picoCTF-shell-manager,RitwikGupta/picoCTF-shell-manager