Follow-up to #13900

I read about sharing IDE config at https://stackoverflow.com/a/9092648/873282 and https://www.jetbrains.com/help/idea/configure-project-settings.html#share-project-through-vcs

This implements sharing using git.

Benefit:

• Users immediately have the code style activated
• Changes in the config - are directly persisted in git and can shared easily.
• Supported by IntelliJ

Note: The filename Project.xml is hard coded.

Other options:

• Export and import settings: https://www.jetbrains.com/help/idea/sharing-your-ide-settings.html?_cl=MTsxOzE7OTRVRlhLb3ZQWXA3TEdjQXlRT3RrYW1jUU1lWDdNN25DNGZnNk53R0h6ZWVTMktiWjVDS1NQYmxhRjF5NkNIWjs%3D#import-export-settings -- more coverage, but harder to review

Steps to test

1. Checkout the branch
2. Restart IntelliJ using cache invalidation
3. Modify something in the code style
4. git diff should show a change in .idea/codeStyles/Project.xml

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.