docs: Add Helm guides

[webvictim]

Updates #5582

Still a work in progress.

[webvictim]

https://teleport-docs-next-nri80bqhs-gravitational.vercel.app/docs/ver/7.0/helm/guides/

[klizhentas]

I've done the first pass. Monumental work. General notes:

• Let's move all the content to Kubernetes access
• Let's split getting started, architecture and reference to separate docs

Ping me if you have any questions, would be happy to discuss over quick chat.

[webvictim]

@klizhentas I've addressed pretty much all your feedback. Just need to write the migration guide and add some details on cert-manager for AWS and GKE.

Vercel: https://teleport-docs-next-git-gus-helmdocs-gravitational.vercel.app/docs/ver/7.0/kubernetes-access/helm/guides/

[webvictim]

cert-manager details have been added. Only thing left is the migration guide, which I'll work on this week.

[webvictim]

@klizhentas Please re-review.

[webvictim]

Migration guide is now added. Docs live at https://teleport-docs-next-git-gus-helmdocs-gravitational.vercel.app/docs/ver/7.0/kubernetes-access/helm/guides/

[webvictim]

@klizhentas Ping

[klizhentas]

@webvictim will review tomorrow, thanks Gus!

[klizhentas]

Overall, solid work, great attention to detail and props for taking care of cert-manager, migration and reference. High quality work, @webvictim well done.

I have a ton of nitpicks, mostly styling and using new features of the docs. Once applied, should be good to go.

[klizhentas]

This does not render as a header, so hard to separate sections from each other. Please try this

## Chart `teleport-cluster`

[webvictim]

This is annoying - it used to render as a header but it stopped when I rebased so clearly this was changed at some point.

[klizhentas]

This has the same level as the helm chart, but is a property of the chart. Let's try this instead and see how it renders

### Parameter `clusterName`

This will also make TOC manageable., right now it overflows.

[webvictim]

A multi-level TOC which uses the level of the header comments would be really nice, or some other way to auto-generate a TOC at the top of the file rather than using the side nav.

[klizhentas]

Nit: sometimes we use $ and sometimes not, probably remove elsewhere too?

[webvictim]

Yeah you're right. My intention is to use $ whenever there is example output after the command (to separate the two) but this one was inconsistent.

[webvictim]

@klizhentas This has addressed the majority of your nits. I'm wondering if there's a better way we can handle the TOC on the reference pages rather than having to manually generate one.

Also, the formatting of fixed-width headers seems to have changed between when I started this PR and now - they used to scale to the size of header used (i.e. when using ## you'd get bigger text) but now for some reason they're all rendered at a fixed size which makes everything look weird. I've raised an issue in next for this: https://github.com/gravitational/next/issues/231

[klizhentas]

@webvictim thank you, will review today.

[klizhentas]

LGTM. 🚢 🚀

[webvictim]

Thanks @klizhentas - could you take a look at #6344 too please? Andrew’s already reviewed the code so mostly needs a code owner stamp.