add file-type requirement and redirect
as suggested by
@@ -210,7 +210,7 @@ The terminal output of commands run from parallel threads using `-x` will not be
so `fd -x` can be used to rudimentarily parallelize a task run over many files.
An example of this is calculating the checksum of each individual file within a directory.
```
-fd -x md5sum
+fd -tf -x md5sum > file_checksums.txt
```
#### Placeholder syntax
