docs: bump action-setup version in README

Author: zkochan

Diff for: README.md

@@ -72,7 +72,7 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
-      - uses: pnpm/action-setup@v3
+      - uses: pnpm/action-setup@v4
         with:
           version: 8
 ```
@@ -91,7 +91,7 @@ jobs:
     steps:
       - uses: actions/checkout@v4
 
-      - uses: pnpm/action-setup@v3
+      - uses: pnpm/action-setup@v4
         with:
           version: 8
           run_install: |
@@ -120,7 +120,7 @@ jobs:
         with:
           node-version: 20
 
-      - uses: pnpm/action-setup@v3
+      - uses: pnpm/action-setup@v4
         name: Install pnpm
         with:
           version: 8