#2833 79545412 Thanks @natemoo-re! - This PR introduces a new internal CSS parser for @astrojs/compiler. See withastro/compiler#329 for more details.

This fixes Astro's support for modern CSS syntax like @container, @layer, and nesting. Note While Astro now correctly parses this modern syntax, it does not automatically compile features for browser compatability purposes.
#2824 0a3d3e51 Thanks @bholmesdev! - Change shiki to our default markdown syntax highlighter. This includes updates to all relevant starter projects that used Prism-specific styles.

#2798 4c25a1c2 Thanks @matthewp! - Implement APIs for headers for SSR flag
#2825 1cd7184c Thanks @hlynursmari1! - Fix island deduplication ignoring props.Re-resolves an issue initially patched in https://github.com/withastro/astro/pull/846 but seemingly lost in the 0.21.0 mega-merge (https://github.com/withastro/astro/commit/d84bfe719a546ad855640338d5ed49ad3aa4ccb4).This change makes the component render step account for all props, even if they don't affect the generated HTML, when deduplicating island mounts.
#2815 7b9d042d Thanks @matthewp! - Allows dynamic routes in SSR to avoid implementing getStaticPaths
Updated dependencies [0a3d3e51]:
- @astrojs/markdown-remark@0.7.0-next.0