chore(release): prepare v0.1.1

[kyerpotts]

Summary

Prepare Vulkanite v0.1.1 after the active-tab, bufferline, and unnecessary-code highlight improvements merged in #4.

• Finalize the v0.1.1 changelog.
• Add release notes consumed by the release script.
• Point the README at the latest release notes.

Verification

• Headless test suite
• Direct colorscheme smoke test
• StyLua and git diff --check
• Manual visual inspection completed in feat: improve tab and unnecessary-code highlights #4

Checklist

• My PR title follows Conventional Commits.
• This change is focused and includes no unrelated cleanup.
• I updated release documentation.
• I read and understand all submitted changes, including AI-assisted work.