Added minimum window sizing for creating new entries

[ityyrm]

Closes #11944

Added minimum sizing for windows to create new entries.

Minimum window size for creating a new entry:

It was also observed that the same issue is present for creating a new entry from plain text, so minimal window sizing was also included for this.:

Mandatory checks

• I own the copyright of the code submitted and I licence it under the MIT license
• 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.

[github-actions]

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[Siedlerchr]

use the fxml for this

[Siedlerchr]

Why don't you simply adjust this in the fxml?

[ityyrm]

I have attempted a simple adjustment to the FXML (specifically setting the minWidth and minHeight properties in the root DialogPane), but it doesn't seem to affect the minimum window size, as the window itself can be resized to smaller than the set values. I believe this is because the FXML is encoding the internals and minimum size of those, while we need to set the minimum size for the stage as a whole. I have looked at incorporating the stage into the FXML, however, even if this path can work it seems to lead to a significantly more convoluted change to achieve the same effect. This also reflects the way it was done for the main stage in JabRefGUI:

jabref/src/main/java/org/jabref/gui/JabRefGUI.java

Lines 209 to 210 in a06804e

	mainStage.setMinWidth(580);
	mainStage.setMinHeight(330);

Please tell me if I have missed something, I am new to FXML and may just be missing something quite obvious.

[koppor]

Since EntryTypeView extends BaseDialog<EntryType>, shouldn't that go into org.jabref.gui.util.BaseDialog#BaseDialog?

@Siedlerchr I see a big unclearness: Why don't the children of BaseDialog call the constructor? Or do I miss some JavaMagic (I would search for super() in the constructors).

[Siedlerchr]

If a constructor body does not begin with an explicit constructor invocation and the constructor being declared is not part of the primordial class Object, then the constructor body implicitly begins with a superclass constructor invocation "super();", an invocation of the constructor of its direct superclass that takes no arguments.

https://docs.oracle.com/javase/specs/jls/se7/html/jls-8.html#jls-8.8.7

[Siedlerchr]

Okay, fine, please fix the checkstyle issue and it's okay from my side
Import jabrefs's code style and select organize imports