Add Fluent 9 theme

[flanakin]

🛠️ Description

Add Fluent 9 theme files

NOTE: We will need to update this later. The colors are not precisely accurate. The theme designer doesn't use the exact base color. Adding this temporarily. We can tweak it later.

📷 Screenshots

See https://react.fluentui.dev/?path=/docs/theme-theme-designer--docs

📋 Checklist

🙋‍♀️ Do any of the following that apply?

• 🚨 This is a breaking change.
• 🤏 The change is less than 20 lines of code.

📑 Did you update docs/changelog.md?

• ✅ Updated changelog (required for dev PRs)
• ➡️ Will add log in a future PR (feature branch PRs only)
• ❎ Log not needed (small/internal change)

📖 Did you update documentation?

• ✅ Public docs in docs (required for dev)
• ✅ Internal dev docs in src (required for dev)
• ➡️ Will add docs in a future PR (feature branch PRs only)
• ❎ Docs not needed (small/internal change)