Add isEmpty() method to check for empty Tiptap content

[putrafajarh]

Background

Currently, there's no straightforward way to check if the content of a Tiptap editor is empty. This can be particularly useful for form validation or preventing submission of empty content.

Proposed Solution

Implement an isEmpty() method for Tiptap that returns a boolean value indicating whether the editor's content is empty or not.

Expected Behavior

• Return true if the editor contains only empty paragraphs or whitespace
• Return false if the editor contains any meaningful content (text, images, etc.)

Use Case

This method would be helpful in scenarios such as:

• Validating form submissions to ensure non-empty content
• Disabling submit buttons when the editor is empty
• Checking if a user has actually entered any content before saving

[putrafajarh]

FYI, there is editor.isEmpty on tiptapjs