Update registry documentation with new proc-macro field.
Update registry documentation with new proc-macro field.

tshepang/cargo,eminence/cargo,nipunn1313/cargo,nipunn1313/cargo,tshepang/cargo,tsurai/cargo,tshepang/cargo,eminence/cargo,eminence/cargo,rust-lang/cargo,vojtechkral/cargo,vojtechkral/cargo,rustyhorde/cargo,rust-lang/cargo,tsurai/cargo,nipunn1313/cargo,tsurai/cargo,rust-lang/cargo,vojtechkral/cargo,rustyhorde/cargo,vojtechkral/cargo,tshepang/cargo,rust-lang/cargo,tsurai/cargo,rustyhorde/cargo,rustyhorde/cargo,eminence/cargo,tsurai/cargo,nipunn1313/cargo