docs: add `Rollup` to showcase (#2128)

docs/guide/what-is-vitepress.md

@@ -12,7 +12,7 @@ Just want to try it out? Skip to the [Quickstart](./getting-started).
 
 - **Documentation**
 
-  VitePress ships with a default theme designed for technical documentation, especially those that need to embed interactive demos. It powers this page you are reading right now, along with the documentation for [Vite](https://vitejs.dev/), [Pinia](https://pinia.vuejs.org/), [VueUse](https://vueuse.org/), [Mermaid](https://mermaid.js.org/), [Wikimedia Codex](https://doc.wikimedia.org/codex/latest/), and many more.
+  VitePress ships with a default theme designed for technical documentation, especially those that need to embed interactive demos. It powers this page you are reading right now, along with the documentation for [Vite](https://vitejs.dev/), [Pinia](https://pinia.vuejs.org/), [VueUse](https://vueuse.org/), [Rollup](https://rollupjs.org/), [Mermaid](https://mermaid.js.org/), [Wikimedia Codex](https://doc.wikimedia.org/codex/latest/), and many more.
 
   The [official Vue.js documentation](https://vuejs.org/) is also based on VitePress, but uses a custom theme shared between multiple translations.