[R20-2027] set default layout background colour

[lambry]

Issue: https://digital-vic.atlassian.net/browse/R20-2027

What I did

• Some accessibility tools allow inverting a page, however without the bg being explicitly set this doesn't work well.

Before

After

Checklist

For all PR's

• I've added relevant changes to the project Readme if needed.
• I've updated the documentation site as needed.
• I have added unit tests to cover my changes (if not applicable, please state why in a comment)

For new components only

• I have added a story covering all variants
• I have checked a11y tab in storybook passes
• Any events are emitted on the event bus

[netlify]

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[cypress]

Passing run #1982 ↗︎

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Details:

feat(@dpc-sdp/ripple-ui-core): set default layout background colour
Project: ripple-framework	Commit: f7d5cc01b8
Status: Passed	Duration: 07:13 💡
Started: Jun 26, 2024 5:27 AM	Ended: Jun 26, 2024 5:34 AM

Review all test suite changes for PR #1237 ↗︎

[waitingallday]

I tried it on that arabic page from https://digital-vic.atlassian.net/browse/SDPAP-9439 as well just out of curiosity, looks good 👍