Improve footer layout on mobile devices

[rohitsrma]

The website's footer section lacks responsiveness on mobile devices. Currently, all options are displayed in a single row regardless of the screen size. I've added a display property to address this issue.

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[knative-prow]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: rohitsrma
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[knative-prow-robot]

PR needs rebase.

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