Add note about teed streams not connected to original stream to docs.

Author: codedread

docs/bitjs.io.md

@@ -81,4 +81,8 @@ pick up where you left off with the original stream.
   const description = teedStream.skip(strOffset).readString(strLen);
 
   const someOtherVal = origStream.readNumber(4); // Bytes 8-11
-```
+```
+
+Note that the teed stream is not "connected" to the original stream. If you push new bytes to the
+original stream, the teed stream does not see them. If you find this behavior unexpected, please
+file a bug.