Add `themeNext` to `ThemeProvider`

[origami-z]

Prep for potential Salt site using theme next

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Name	Status	Preview	Comments	Updated (UTC)
mosaic	✅ Ready (Inspect)	Visit Preview	💬 Add feedback	Jul 1, 2024 9:58pm

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🦋 Changeset detected

Latest commit: 25a9871a201dd9ae8e9a3a5b3012d87c4c0585d9

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 28 packages

| Name | Type | | ------------------------------------------- | ----- | | @jpmorganchase/mosaic-components | Minor | | @jpmorganchase/mosaic-site-preset-styles | Minor | | @jpmorganchase/mosaic-cli | Minor | | @jpmorganchase/mosaic-labs-components | Minor | | @jpmorganchase/mosaic-content-editor-plugin | Minor | | @jpmorganchase/mosaic-core | Minor | | @jpmorganchase/mosaic-create-site | Minor | | @jpmorganchase/mosaic-from-http-request | Minor | | @jpmorganchase/mosaic-layouts | Minor | | @jpmorganchase/mosaic-open-api-component | Minor | | @jpmorganchase/mosaic-plugins | Minor | | @jpmorganchase/mosaic-schemas | Minor | | @jpmorganchase/mosaic-serialisers | Minor | | @jpmorganchase/mosaic-site-components | Minor | | @jpmorganchase/mosaic-site-middleware | Minor | | @jpmorganchase/mosaic-site | Minor | | @jpmorganchase/mosaic-sitemap-component | Minor | | @jpmorganchase/mosaic-source-figma | Minor | | @jpmorganchase/mosaic-source-git-repo | Minor | | @jpmorganchase/mosaic-source-http | Minor | | @jpmorganchase/mosaic-source-local-folder | Minor | | @jpmorganchase/mosaic-source-readme | Minor | | @jpmorganchase/mosaic-source-storybook | Minor | | @jpmorganchase/mosaic-standard-generator | Minor | | @jpmorganchase/mosaic-store | Minor | | @jpmorganchase/mosaic-theme | Minor | | @jpmorganchase/mosaic-types | Minor | | @jpmorganchase/mosaic-workflows | Minor |

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