Situate the Installation guide more clearly (#9524)
Situate the Installation guide more clearly (#9524)

* Situate the Installation guide more clearly

For a reader who begins their journey through the Teleport docs
with the Installation guide, it can be difficult to determine
what to do after following the guide. This change makes the
relationship between the Installation page and other docs pages
clearer by:

- Adding an Admonition to read the Getting Started guides if you
  have not yet tried Teleport. These guides include installation
  instructions, so they can be our recommended starting place.

- Adding a Next Steps section that links to instructions on
  enabling Teleport for different infrastructure resources.

Closes #9355

* Respond to PR feedback
gravitational/teleport,gravitational/teleport,gravitational/teleport,gravitational/teleport,gravitational/teleport,gravitational/teleport