fix: www homepage background gradient

[stephiescastle]

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Description

Fixes

• Background gradient not showing in WWW Homepage slides #638

Changes

• it was assumed that to-black would work for all viewports. However, since different viewports have different from values, we also need to specify their respective to values

Instructions to test

1. make vue-storybook
2. confirm there is a visible background gradient: http://localhost:6006/?path=/story/components-www-homepage-homepagecarousel--base-story

Tested in the following environments/browsers:

Operating System

• macOS
• iOS
• iPadOS
• Windows

Browser

• Chrome
• Firefox ESR
• Firefox
• Safari
• Edge