some milestones for 2.0

Build

• feat(2.0)!: remove mdxRs temporarily in loader and @rspress/modern-js-plugin #1851
• add rehype-raw to mdx-loader
• migrate from prism to shiki
• pure esm infra
• update shiki packages feat!(plugin-shiki): bump shiki to v3, migrate to official transformers #1672
• update mdxjs related packages
• only extract toc and pageSearch with flattenMdx

Theme

• feat(theme)!: use named export instead of default export, for circular imports #1873
• npm package
• [Rspress 2.0][Theme]: tailwindcss isolated #1967

...

TODO