docs(README): document new config option added in #257

Author: NTBBloodbath

README.md

@@ -67,6 +67,8 @@ use {
       result_split_horizontal = false,
       -- Keep the http file buffer above|left when split horizontal|vertical
       result_split_in_place = false,
+      -- stay in current windows (.http file) or change to results window (default)
+      stay_in_current_window_after_split = false,
       -- Skip SSL verification, useful for unknown certificates
       skip_ssl_verification = false,
       -- Encode URL before making request