Adjust Line Break Policy and Add Shift+Enter Functionality

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Changes Made:

1. Adjusted the settings to disallow the preservation of line breaks. Line breaks are no longer permitted, following a similar policy to Notion's callout feature.
2. Implemented functionality to allow users to add line breaks using the Shift+Enter combination.

Reasons for Changes:

The previous line break policy could lead to unexpected confusion among users. By adopting a policy similar to Notion's callout feature, users will experience a more consistent editing environment. Additionally, the implementation of Shift+Enter functionality provides users with the flexibility to add line breaks only when necessary.

Before Changes:

• Line breaks were preserved within text, potentially resulting in discrepancies between the edited and rendered content.

After Changes:

• A policy similar to Notion's callout feature has been adopted, ensuring a more consistent user experience.
• Users can utilize Shift+Enter to add line breaks as needed.

Additional Information:

These changes aim to enhance user convenience and provide a more consistent editing environment. We anticipate that these modifications will have a positive impact on user experience.