Support pnpm in template actions

[Shion1305]

Summary

Template implementations do not support using pnpm as the package manager. We need support for pnpm.

Details

This repository contains steps for detecting the package manager and configuring the tool based on its package manager environment.

      - name: Detect package manager
        id: detect-package-manager
        run: |
          if [ -f "${{ github.workspace }}/yarn.lock" ]; then
            echo "manager=yarn" >> $GITHUB_OUTPUT
            echo "command=install" >> $GITHUB_OUTPUT
            echo "runner=yarn" >> $GITHUB_OUTPUT
            exit 0
          elif [ -f "${{ github.workspace }}/package.json" ]; then
            echo "manager=npm" >> $GITHUB_OUTPUT
            echo "command=ci" >> $GITHUB_OUTPUT
            echo "runner=npx --no-install" >> $GITHUB_OUTPUT
            exit 0
          else
            echo "Unable to determine package manager"
            exit 1
          fi

One of the most modern node package managers, pnpm, is very popular among many repositories. There are potential demands for integrating pnpm in GitHub Actions. We should add support for pnpm so that projects with pnpm can easily introduce actions using templates.