[WIP] Initial framework for jablib-examples

[koppor]

With the modularization we got "jablib". Now, its time to offer it as "useful" library.

I tried to write some scripts in JBang, but the API of JabRef was less than OKish, so I refactored.

Aim for this PR:

• Extract references from PDF
• DOI to BibTeX

WIP

Additional Changes

IEEE as explicit rule-based parser available

Mandatory checks

• I own the copyright of the code submitted and I license it under the MIT license
• I manually tested my changes in running JabRef (always required)
• I added JUnit tests for changes (if applicable)
• I added screenshots in the PR description (if change is visible to the user)
• I described the change in CHANGELOG.md in a way that is understandable for the average user (if change is visible to the user)
• I checked the user 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 updating file(s) in https://github.com/JabRef/user-documentation/tree/main/en.