Update Installation to better orient users

Overview

The installation instructions are generally very good, but there are a few speed bumps to finding and performing the right installation procedure.

Add "roadmap" information to orient readers in the Installation section of the documentation.

Audience: Admins and developers

Type: Instructional

Context

This issue tracks recommended changes resulting from an analysis of the Knative documentation commissioned by CNCF. The analysis and supporting documents are here: https://github.com/cncf/techdocs/tree/main/analyses under 0015-knative.

Possible Implementation

Related material in the current doc:

• https://github.com/knative/install

Suggested changes:

On the [Installing Knative] page, provide a roadmap at the top to direct users to the correct installation. Aside from installing the different components (Eventing and Serving) using different modalities (YAML, Kubernetes Operator, and upgrading), disclose what operating systems are supported, and differentiate between local and server installations.