Migration from v5 (#1548)

* Migration from v5

* ドメイン変更

* docs: add some migration guide for v6

* fix!: default `build.cssMinify` to `'esbuild'` for SSR

* feat(css)!: change default sass api to modern/modern-compiler

* docs: migration guide for plugin-commonjs upgrade

* chore(deps)!: update postcss-load-config to v6

Author: jay-es

.vitepress/config.ts

@@ -297,7 +297,7 @@ export default defineConfig({
               link: '/guide/philosophy',
             },
             {
-              text: 'v4 からの移行',
+              text: 'v5 からの移行',
               link: '/guide/migration',
             },
             {