Fix dev commands, use pnpm instead of yarn (#60)

Co-authored-by: Wu Jianbo <[email protected]>

Author: t1ger-0527

README.md

@@ -12,8 +12,8 @@ This is a demo app of the Hacker News website clone, which shows Next.js 13's `a
 
 ### Running Locally
 
-1. `yarn install`
-2. `yarn dev`
+1. `pnpm install`
+2. `pnpm dev`
 
 Go to `localhost:3000`.