Improve readability of global.json creation command (#694)

Updated the command to create global.json for better readability and execution.

README.md

@@ -239,7 +239,8 @@ jobs:
         with:
           dotnet-version: ${{ matrix.dotnet }}
       - name: Create temporary global.json
-        run: echo '{"sdk":{"version": "${{ steps.stepid.outputs.dotnet-version }}"}}' > ./global.json
+        run: |
+          echo '{"sdk":{"version": "${{ steps.stepid.outputs.dotnet-version }}"}}' > ./global.json
       - name: Execute dotnet
         run: dotnet build <my project>
 ```