Documentation on setting up CHT on k3s

[esthermmoturi]

Per parent ticket: this ticket does not mean adding steps for setting up k3s from scratch. That should be in the prerequisites and just be "set up k3s per our requirements page"

It should:

• be placed under the kubernetes folder on the docs site as _index.md so when you click the kubernetes you end up there - just like it is for docker link (via this index file)
• should cover TLS set up using free Let's Encrypt certs
• as much default configuration as possible (no weird custom setups of k3s that would be unexpected)
• follows a happy path - only document the way to a running CHT Core instance, not every possible side path to get there
• has lots of copy and paste-able commands!

[mrjones-plip]

@esthermmoturi - this was the old description, but I think it's incorrect - please let me know if I shouldn't have removed this:

This is a generic guide that instructs users on how to install k3s. It should provide an overview and specifications to different components of K3s.

@ernestoteo is hoping to work on this on Monday so please ping me if this needs any corrections.