chore: update pnpm to 8 and and node@20 in ci (#552)

This PR aims to reach the following results:
- pnpm to v8
- add node v20 to ci
- make vercel playground work well after upgrading pnpm to v8(need
@shuding access to the vercel dashboard to make it deploy well)

@shuding Thanks for your time~

.github/workflows/ci.yml

@@ -40,7 +40,7 @@ jobs:
       fail-fast: false
       matrix:
         os: [ubuntu-latest]
-        node: [16, 18]
+        node: [16, 18, 20]
     runs-on: ${{ matrix.os }}
     steps:
       - name: Checkout

package.json

@@ -115,7 +115,7 @@
     "postcss-value-parser": "^4.2.0",
     "yoga-wasm-web": "^0.3.3"
   },
-  "packageManager": "pnpm@7.11.0",
+  "packageManager": "pnpm@8.7.0",
   "engines": {
     "node": ">=16"
   }