#368 Fix line advancement after node props

[fktn-k]

This PR has fixed a bug reported in #368 as well as related, underlying ones by modifying implementation for parsing node properties.
The major bugs are as follows:

• no line advancement happens after parsing node properties for mappings as a block sequence entry (the reported bug),
• no parsing happens for mapping values whose node properties are user defined (i.e., neither !!map nor the likes), and
• incorrect node traversal to select a mapping key node with a desired indentation.

---

Pull Request Checklist

Read the CONTRIBUTING.md file for detailed information.

• [x] Changes are described in the pull request or in a referenced issue.
• [x] The test suite compiles and runs without any error.
• [x] The code coverage on your branch is 100%.
• [x] The documentation is updated if you added/changed a feature.

Please don't

• The C++11 support varies between different compilers and versions. Please note the list of supported compilers. Some compilers like GCC 4.7 (and earlier), Clang 3.3 (and earlier), or Microsoft Visual Studio 13.0 and earlier are known not to work due to missing or incomplete C++11 support. Please refrain from proposing changes that work around these compiler's limitations with #ifdefs or other means.
• Please refrain from proposing changes that would break YAML specifications. If you propose a conformant extension of YAML to be supported by the library, please motivate this extension.
• Please do not open pull requests that address multiple issues.

[github-actions[bot]]

:octocat: Upload Coverage Event Notification

Coverage data has been uploaded for the commit 4ca8a819282ddc84391833f763e8f5e3ec2be946. You can download the artifact which contains the same file uploaded to the Coveralls and its HTML version.

Name	fkYAML_coverage.pr369.zip
ID	1822339841
URL	https://github.com/fktn-k/fkYAML/actions/runs/10429213467/artifacts/1822339841