fixed some style issues, added tooling for docs

docs/hosts/subscriber.md

@@ -0,0 +1,8 @@
+# hosts/subscriber.h
+
+## class Publisher — public interface
+
+### `virtual void recv_mgmt_msg(MgmtMsgPtr msg) noexcept override;`
+### `void recv_frame(const Packet& frame) override;`
+### `void set_status(NodeStatus s) noexcept;`
+### `void set_publisher(Publisher* p) noexcept { ... }`