Make install downloads findable

[dwelsch-esi]

Overview

Currently the binary install download links in the Installing section redirect
to the release notes, where the list of download files is far down the page.
Move and relabel the download file sectionm so that the files are easy to find.

Audience: All

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://knative.dev/docs/install/quickstart-install/#__tabbed_1_2
• https://knative.dev/docs/client/install-kn/#__tabbed_1_2
• https://knative.dev/docs/install/operator/knative-with-operator-cli/#__tabbed_1_1
• https://knative.dev/docs/install/operator/knative-with-operator-cli/#__tabbed_1_2
• https://github.com/knative/client/releases

Suggested changes:

Move the install download links to the top of the Release Notes or clearly link
to them from the top of the Release Notes. Or, put them on their own Downloads
page.

Rename the heading for the download files from "Assets" to "Downloads" or
"Install files