Add support for HAProxy

[nathankot]

I can update the documentation if there is appetite for this :)
Note I haven't tested this with klipperlb

[mysticaltech]

@nathankot This is great, thanks! Please add some docs, same as for the others, especially readme and kube.tf.example tweaks and will merge 🙏

[mysticaltech]

Please apart from docs, also apply terraform format, the command or use the terraform vscode extension to get the format right. Either way will work.

[nathankot]

@mysticaltech i've run fmt and updated the example/readme files, looks like there is a github bot that updates the the terraform.md file so didn't touch that :)

[mysticaltech]

Thanks @nathankot, looking good to fly! 🚀 🙏