add example with multiple filters to readme.

README.md

@@ -28,6 +28,11 @@ pool.sub({cb:(event, relay) => {...}, filter: {authors: ['<hex1>', '<hex2>', ...
 
 // get specific event
 pool.sub({cb: (event, relay) => {...}, filter: {id: '<hex>'}})
+// or get a specific event plus all the events that reference it in the 'e' tag
+pool.sub({
+  cb: (event, relay) => {...},
+  filter: [{id: '<hex>'}, {'#e': '<hex>'}]
+})
 
 // get all events
 pool.sub({cb: (event, relay) => {...}, filter: {}})