docs: upgrades to vite core (#9070)

Author: patak-dev

docs/blog/announcing-vite3.md

@@ -237,6 +237,17 @@ A triaging marathon was spearheaded by [@bluwyoo](https://twitter.com/bluwyoo),
 
 Learn more in the [Migration Guide](/guide/migration).
 
+## Upgrades to Vite Core
+
+While working towards Vite 3, we also improved the contributing experience for collaborators to [Vite Core](https://github.com/vitejs/vite).
+
+- Unit and E2E tests have been migrated to [Vitest](https://vitest.dev), providing a faster and more stable DX. This move also works as dog fooding for an important infrastructure project in the ecosystem.
+- VitePress build is now tested as part of CI.
+- Vite upgraded to [pnpm 7](https://pnpm.io/), following the rest of the ecosystem.
+- Playgrounds have been moved to [`/playgrounds`](https://github.com/vitejs/vite/tree/main/playground) out of packages directory.
+- The packages and playgrounds are now `"type": "module"`.
+- Plugins are now bundled using [unbuild](https://github.com/unjs/unbuild), and [plugin-vue-jsx](https://github.com/vitejs/vite/tree/main/packages/plugin-vue-jsx) and [plugin-legacy](https://github.com/vitejs/vite/tree/main/packages/plugin-legacy) were moved to TypeScript.
+
 ## The Ecosystem is Ready for v3
 
 We have worked closely with projects in the ecosystem to ensure that frameworks powered by Vite are ready for Vite 3. [vite-ecosystem-ci](https://github.com/vitejs/vite-ecosystem-ci) allows us to run the CI's from the leading players in the ecosystem against Vite's main branch and receive timely reports before introducing a regression. Today's release should soon be compatible with most projects using Vite.
@@ -250,6 +261,7 @@ We want to thank everyone that have implemented features, and fixes, given feedb
 - Vite team members [@youyuxi](https://twitter.com/youyuxi), [@patak_dev](https://twitter.com/patak_dev), [@antfu7](https://twitter.com/antfu7), [@bluwyoo](https://twitter.com/bluwyoo), [@sapphi_red](https://twitter.com/sapphi_red), [@haoqunjiang](https://twitter.com/haoqunjiang), [@poyoho](https://github.com/poyoho), [@Shini_92](https://twitter.com/Shini_92), and [@retropragma](https://twitter.com/retropragma).
 - [@benmccann](https://github.com/benmccann), [@danielcroe](https://twitter.com/danielcroe), [@brillout](https://twitter.com/brillout), [@sheremet_va](https://twitter.com/sheremet_va), [@userquin](https://twitter.com/userquin), [@enzoinnocenzi](https://twitter.com/enzoinnocenzi), [@maximomussini](https://twitter.com/maximomussini), [@IanVanSchooten](https://twitter.com/IanVanSchooten), the [Astro team](https://astro.build/), and all other maintainers of frameworks and plugins in the ecosystem in that helped shape v3.
 - [@dominikg](https://github.com/dominikg) for his work on vite-ecosystem-ci.
+- [@ZoltanKochan](https://twitter.com/ZoltanKochan) for his work on [pnpm](https://pnpm.io/), and for his responsivness when we needed support with it.
 - [@rixo](https://github.com/rixo) for HMR Partial Accept support.
 - [@KiaKing85](https://twitter.com/KiaKing85) for getting the theme ready for the Vite 3 release, and [@\_brc_dd](https://twitter.com/_brc_dd) for working on the VitePress internals.
 - [@CodingWithCego](https://twitter.com/CodingWithCego) for the new Spanish translation, and [@ShenQingchuan](https://twitter.com/ShenQingchuan), [@hiro-lapis](https://github.com/hiro-lapis) and others in the Chinese and Japanese translations teams for keeping the translated docs up to date.