Add Astro Keel (portfolio + blog theme)

[kpab]

Adds Astro Keel to the Repositories/Starter Kits/Components section.

Astro Keel is a minimal, neutral portfolio + blog theme for Astro 7 (MIT licensed):

• One-line accent color — the whole theme retunes from a single CSS variable
• Light/dark mode with no flash on load
• Content Collections (works + blog), tags, per-post table of contents, RSS
• Shiki dual-theme syntax highlighting, self-hosted fonts, sitemap/OG out of the box
• Live demo: https://kpab.github.io/astro-keel/ (also listed in the official Astro themes catalog)

Thanks for the great list!