Add support for pnpm/action-setup with version: updates

[rarkins]

Discussed in #34724

^{Originally posted by alexfaxe March 10, 2025}

Tell us more.

Similar to the recent feature addition done in #34658

The github-actions manager should be updated to extract the version value when using pnpm/action-setup.

Example syntax:

- name: Setup pnpm
      uses: pnpm/action-setup@v4
      with:
        version: 10.6.1
```</div>


Use datasource=npm and packageName=pnpm

[viceice]

workaround: configure pnpm version inside packageManager field of package.json and let the action read the version from there.

renovate/.github/actions/setup-node/action.yml

Lines 50 to 53 in 7df08e1

	- name: Setup pnpm
	uses: pnpm/action-setup@a7487c7e89a18df4991f7f222e4898a00d66ddda # v4.1.0
	with:
	standalone: true