docs: add backup reader protocol

src/bin/dump-reader-api.rs

@@ -0,0 +1,13 @@
+use failure::*;
+
+use proxmox_backup::api2;
+use proxmox_backup::api_schema::format::*;
+
+fn main() -> Result<(), Error> {
+
+    let api = api2::reader::READER_API_ROUTER;
+
+    dump_api(&mut std::io::stdout(), &api, ".", 0)?;
+
+    Ok(())
+}