Update readme

README.md

@@ -6,6 +6,7 @@ kažy is an application that highlights, filters and extracts string patterns fr
 
 ### How to use?
 ```
+$ kazy -h
 Highlights, filters and extracts string patterns from STDIN
 
 Usage:
@@ -14,7 +15,7 @@ Usage:
 Flags:
   -b, --buffer int            buffer size in KB (default 64)
   -e, --exclude stringArray   exclude from output lines which match provided patterns
-  -x, --extract               extract matched strings (leftmost) instead of highlighting them
+  -x, --extract count         extract instead of highlighting. Can be provided multiple times to control which matched string is extracted
   -h, --help                  help for kazy
   -i, --include stringArray   only include lines which match provided patterns
   -l, --limit int             limit the length of the line, characters