docs: add paths_released output and a link for manifest effects on outputs

[ehakan]

Changes summary:

• Documented the paths_released output from feat: output list of paths released during manifest release #362.
• Added a note pointing from Outputs section to the Manifest release outputs section.

I only ever used release-please and release-please action with manifests, I think it's a good change to highlight the extent of side-effects manifest has on outputs. Personally, I didn't even see that section before my monorepo workflow started failing with empty strings.

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[ehakan]

Signed the CLA

[chingor13]

Thank you for this. In the v4 refactor, paths_released was documented.