Fixes #10415.

1. Remove unwanted leading and trailing whitespaces while adding the selected text to list, as required in Step 6.
2. Remove unwanted empty brackets while formatting the text, as required in Step 14.
3. Allow the user to add the word at the cursor, as required in Step 4. For example,
   
   
   

Mandatory checks

• 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.