Document - New preference option to add files in Entry Editor

[shahamish150294]

Under https://help.jabref.org/en/EntryEditor, add documentation to explain in detail the three different behaviors when file(s) are dragged and dropped in the entry editor. These behaviors can be set by the user through Preferences.
Issue: JabRef/jabref#4356
PR: JabRef/jabref#4408

[shahamish150294]

Consider the following while addressing this issue:

• Actual Behavior
• Different operating systems

[michizhou]

Hi @shahamish150294! If it's no trouble, I'd love to take on this issue. If there is supplemental info besides the issue, PR, or other links already on this page that could help me get started, I would appreciate it if you could kindly provide them. Thanks!

[shahamish150294]

Hi @michizhou feel free to work on this issue. All the related and helpful links to the task are mentioned in the description. Thank you!