Added Hayagriva YAML export

[JawadTUE]

Fixes #10382

I added Hayagrive YAML export based on their documentation.

The following fields are not included, because I did not find a relevant field for them in Jabref: parent, affiliated, issue, volume-total, page-total, time-range, runtime, serial-number, language, archive, archive-location.

HayagrivaType.java contains the mapping from Jabref type to Hayagriva Entry Type.

I confirmed that the exported .yaml file works with the typst system by using hayagriva literature.yml reference as stated in their documentation.

Mandatory checks

• Change in CHANGELOG.md described in a way that is understandable for the average user (if applicable)
• Tests created for changes (if applicable)
• Manually tested changed features in running JabRef (always required)
• Screenshots added in PR description (for UI changes)
• Checked developer's documentation: Is the information available and up to date? If not, I outlined it in this pull request.
• Checked documentation: Is the information available and up to date? If not, I created an issue at https://github.com/JabRef/user-documentation/issues or, even better, I submitted a pull request to the documentation repository.

[Siedlerchr]

I think this looks already good. However, I think it's not necessary to have the own author formatter as they say they can be specified either in square brackets or in verbose mode with multiple authors under each other:

jabref/src/main/resources/resource/layout/yaml.layout

Lines 3 to 6 in 3f53201

	\begin{author}
	author:
	- literal: "\author"
	\end{author}

could be reused here as well? (except the "literal")

Edit// Parent could refer to the crossref (e.g. inbook -> book) field in JabRef, but I don't know if or how this can be used in layouts. I would leave this out.

[Siedlerchr]

Can you also please add a test for this? See the YamlExporterTest as an example

[Siedlerchr]

@JawadTUE How is the status here? Codewise it looked already good. Just unit tests missing

[JawadTUE]

I will finish this by tomorrow.

[JawadTUE]

I added the unit tests. These are basically the same as the tests in YamlExporterTest.java, with one extra test exportsCorrectMultipleAuthors to test that multiple authors are correctly exported.