Add smoke test for npm maintainer encoding (PR #14638)

[v-HaripriyaC]

What are you trying to accomplish?

Add smoke test coverage for dependabot-core#14638, which fixes broken Markdown links in the Maintainer changes section of Dependabot PR bodies when an npm releaser name contains spaces or other URL-unsafe characters (e.g., "GitHub Actions"). Addresses dependabot-core#14595.

The test validates end-to-end that:

• npm_and_yarn can analyse a package with a space-containing npm maintainer name.
• The generated PR body contains a properly percent-encoded link (https://www.npmjs.com/~GitHub%20Actions) rather than the broken unencoded form.

Anything you want to highlight for special attention from reviewers?

• Dependency choice: npm-package-json-lint@9.0.0 is used specifically because the npm registry fixture in dependabot-core#14638 records version 10.0.0 as being published by "GitHub Actions" (with a space), making it the minimal reproducible case.
• Fixtures: npm/maintainer-spaces/package.json and package-lock.json pin the dependency to 9.0.0 so Dependabot proposes the 9.0.0 → 10.0.0 update and reaches the maintainer encoding path.
• The smoke test YAML (tests/smoke-npm-maintainer-spaces.yaml) will need to be regenerated with the final merged commit SHA from dependabot-core#14638 before this PR is ready to merge.
• Currently the test output contains a job_repo_not_found record because the commit SHA is a placeholder; this will be replaced with the real expected output after regeneration.

How will you know you've accomplished your goal?

• Smoke test regenerates cleanly against the merged dependabot-core#14638 commit.
• The regenerated output contains a create_pull_request event whose PR body includes https://www.npmjs.com/~GitHub%20Actions (percent-encoded).
• All existing smoke tests continue to pass.

Checklist

• I have run the complete test suite to ensure all tests and linters pass.
• I have thoroughly tested my code changes to ensure they work as expected, including adding additional tests for new functionality.
• I have written clear and descriptive commit messages.
• I have provided a detailed description of the changes in the pull request, including the problem it addresses, how it fixes the problem, and any relevant details about the implementation.
• I have ensured that the code is well-documented and easy to understand.