Merge entry buttons

[tohfas]

Description of Changes

We have made several enhancements to streamline the user interface and improve usability based on the discussed issue. The key changes include:

1. Merged Buttons
   Consolidated the existing buttons related to adding new entries into a single button. This reduces UI clutter and confusion for newcomers while retaining all essential functionality. The merged dialog now provides multiple tabs for different types of entry creation, including:

2. Implemented Key Bindings
   Key binding functionalities have been enhanced and new bindings added for the features

   • Ctrl+Shift+N for "New entry from text"

3. Modified Dialog Box Size
   The size of the "New entry" dialog has been adjusted to be wider (1000px) to better accommodate the multiple tabs and improve readability on different screen sizes.

Reason for Changes

These changes were implemented to:

• Reduce complexity in the user interface by merging overlapping functionalities
• Improve efficiency for experienced users through key bindings
• Enhance visual accessibility with a larger dialog box

Link to the Closed Issue

Closes #8808

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.

[Siedlerchr]

The width is way too large, please make it half the size

[tohfas]

The width is way too large, please make it half the size

Hi @koppor. This is done, changed it to 500px (half of 1000px). Thanks.

[koppor]

Does not fix the issue.

Read again #8808 (comment)

One modal. Title: "New entry" (base on the code of dialog "Select entry type"

---

Currently, there are four buttons: