docs: typescript tips for using Type-Only Imports and Export (vitejs#6260)

Author: ygj6

docs/guide/features.md

@@ -34,6 +34,13 @@ Vite only performs transpilation on `.ts` files and does **NOT** perform type ch
 
 Vite uses [esbuild](https://github.com/evanw/esbuild) to transpile TypeScript into JavaScript which is about 20~30x faster than vanilla `tsc`, and HMR updates can reflect in the browser in under 50ms.
 
+Use the [Type-Only Imports and Export](https://www.typescriptlang.org/docs/handbook/release-notes/typescript-3-8.html#type-only-imports-and-export) syntax to avoid potential problems like type-only imports being incorrectly bundled. for example:
+
+```ts
+import type { T } from 'only/types'
+export type { T }
+```
+
 ### TypeScript Compiler Options
 
 Some configuration fields under `compilerOptions` in `tsconfig.json` require special attention.