update readme with timeout usage

README.md

@@ -120,11 +120,12 @@ The resulting product is a fully-automated Ubuntu installer. This serves as an e
 | -m  | --meta-data| Path to meta-data file. Will be an empty file if not specified and using the `-a` flag. You may read more about providing a `meta-data` file [HERE](https://cloudinit.readthedocs.io/en/latest/topics/instancedata.html)|
 | -x  | --extra-files| Specifies a folder with files and folders, which will be copied into the root of the iso image. If not set, nothing is copied. Requires use of `--privileged` flag when running in docker|
 | -k  | --no-verify| Disable GPG verification of the source ISO file. By default SHA256SUMS-<current date> and SHA256SUMS-<current date>.gpg files in the script directory will be used to verify the authenticity and integrity of the source ISO file. If they are not present the latest daily SHA256SUMS will be downloaded and saved in the script directory. The Ubuntu signing key will be downloaded and saved in a new keyring in the script directory.|
-|-o   | --offline-installer|   Run a bash script to customize image, including install packages and configuration. It should be used with -x, and the bash script should be avilable in the same extras directory.|
+| -o  | --offline-installer|   Run a bash script to customize image, including install packages and configuration. It should be used with -x, and the bash script should be avilable in the same extras directory.|
 | -r  | --use-release-iso| Use the current release ISO instead of the daily ISO. The file will be used if it already exists.|
 | -s  | --source| Source ISO file. By default the latest daily ISO for Ubuntu 20.04 will be downloaded  and saved as `script directory/ubuntu-original-current date.iso` That file will be used by default if it already exists.|
+| -t  | --timeout | Set the GRUB timeout. Defaults to 30. |
 | -d  | --destination |      Destination ISO file. By default script directory/ubuntu-autoinstall-current date.iso will be created, overwriting any existing file.|
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 ## Sources 
 
 This project is made possible through the open-source work of the following authors and many others. Thank you all for sharing your time, effort, and knowledge freely with us. You are the giants upon whos shoulders we stand. :heart: