Fix muddling of words in readme

Author: stecman

README.md

@@ -18,7 +18,7 @@ qgroupid         rfer         excl
 ```
 
 This script saves looking up path information with `btrfs subvolume list` as paths
-are included added the output:
+are added to the output:
 
 ```
 $ ./btrfs-subvolumes.py /mnt/somebtrfsvol --human-readable --sort=-excl