Update mkllfs docs

docs/mkllfs.md

@@ -22,6 +22,10 @@ Available options:
   -v, --version        print the version of mkllfs and the llfs library that it generates for
 ```
 
+### Using the batch file
+The `mkllfs.bat` file can be used to generate the `llfs_data.c` file from the data in the `llfs-data` directory.
+Before using this script, place mkllfs.exe in the same directory as the batch file.
+
 ## Building
 The mkllfs utility can be built using the following command:
 ```bash