Add package.json to node-version-file list of examples.

[TWiStErRob]

Description:
Add package.json to node-version-file list of examples, because that file is very wide-spread in documentation around the internet for storing versions. Without this change, there's no mention of this possibility in the readme/action.yml file.

The functionality already exists:

setup-node/src/util.ts

Line 10 in 8f152de

if (!nodeVersion) nodeVersion = JSON.parse(contents).engines?.node;

With tests:

setup-node/__tests__/main.test.ts

Line 103 in 8f152de

${'{"engines": {"node": "17.0.0"}}'} | ${'17.0.0'}

Related issue: None.

Check list:

• Mark if documentation changes are required.
• Mark if tests were added or updated to cover the changes.