Document kured integration

[jackfrancis]

After these PRs merge:

• always drain before reboot kubereboot/kured#294
• add node annotations to identify kured reboot operations kubereboot/kured#296

Let's document kured as an officially recommended solution for enforcing automatic reboots on your cluster, and how to integrate its node annotations with the kamino vmss-prototype annotation configurations.

[Michael-Sinz]

We can even set the default values in the values file for the chart to match the Kured values if we want to make Kured integration easy.

I have them in the values.yaml as comments but they could be set by default rather than requiring the user to set them.

In other words, make the Kured integration "easy" by default. (And it is effectively documented in the values.yaml today, we just need to show the full end-to-end "use" in the readme/documentation.)