Adds a browse button next to the path text field for aux-based groups

[samiyac]

Fixes #4586
Added a browse button for aux-based groups.

---

• Change in CHANGELOG.md described
• Tests created for changes
• Manually tested changed features in running JabRef
• Screenshots added in PR description (for bigger UI changes)
• Ensured that the git commit message is a good one
• Check documentation status (Issue created for outdated help page at help.jabref.org?)

[samiyac]

I am relatively new to contributing to FOSS. Could one help me understand why the check failed and how I can resolve it?

[Siedlerchr]

Thanks for your contribution! The code looks so far, just some minor changes

[Siedlerchr]

@samiyac

I am relatively new to contributing to FOSS. Could one help me understand why the check failed and how I can resolve it?

The failing check codecov refers to the Code Coverage, e..g how much of the code functionality is covered with tests. You can ignore it in most cases. We only tend to write tests for the most important parts (e.g. the classes in logic/model) and not for GUI dialogs.
Only if the Travis CI fails, you should check the details and see where and what error occurred, as this executes the checkstyle and the integration tests.

[tobiasdiez]

Thanks for the quick follow-up. Code looks good to me now so I'll merge.