docs: add notes about upstream rtorrent json-rpc (#845)

Author: trim21

README.md

@@ -15,6 +15,20 @@ Flood is a monitoring service for various torrent clients. It's a Node.js servic
 | [Transmission](https://github.com/transmission/transmission)    | :white_check_mark: ([tested](https://github.com/jesec/flood/blob/master/server/.jest/transmission.setup.js)) |
 | [Deluge](https://github.com/deluge-torrent/deluge) v2+          | :alembic: Experimental                                                                                       |
 
+##### RTorrent Notes
+
+For now, rakshasa/rtorrent and jesec/rtorrent are both supported.
+
+If you are using rakshasa/rtorrent>0.15.1 (upstream rtorrent with json-rpc support),
+you will need to add these options to your config:
+
+```ini
+method.redirect=load.throw,load.normal
+method.redirect=load.start_throw,load.start
+method.insert=d.down.sequential,value|const,0
+method.insert=d.down.sequential.set,value|const,0
+```
+
 #### Integrating with Flood
 
 APIs are officially documented inline by the [comments](https://github.com/jesec/flood/blob/f7019001dd81ee8401c87d4c4cd6da6f5f520611/server/routes/api/torrents.ts#L106-L117) and [types](https://github.com/jesec/flood/blob/f7019001dd81ee8401c87d4c4cd6da6f5f520611/shared/schema/api/torrents.ts#L10-L32).