Add a "Trusted by" section to the homepage

[omerbensaadon]

One thing that came up in User Interviews is people using Knative because other large companies (VMware, Google, IBM, etc.) are using Knative.

Let's show this off on the website! I genuinely think it will promote adoption among vendors + users.

CC: @julz @RichieEscarez

[omerbensaadon]

Will also allow vendors to link to their offerings from the homepage, instead of the often neglected https://knative.dev/docs/knative-offerings/

[omerbensaadon]