Issue-203: Drag and Drop posts within editor

[mogmarsh]

Summary

Implements drag and drop functionality for posts within the editor to make moving a pinned post from one slot to another easier. Fixes #203.

Test Plan

• Ensure each Post block has a drag handle or uses the Gutenberg one if possible.
• Confirm each Post block acts as a drop zone.
• Test the drag action includes a payload with the Post ID, any Post customizations, and the block ID of the Post being dragged.
• Verify on drop, the Post info in the payload is set on the receiving block, and the pinned post is removed from the originating block via the block ID.
• Drag and drop should not affect the layout or any block attributes such as class names.
• Check if a post was previously pinned in the receiving block, it is properly handled.
• Improved the cancel and move process for a smoother drag and drop experience.
• Fixed an issue where moving a post did not work as expected.
• Removed the click handler to ensure that drag and drop functionality is streamlined and intuitive.

Screenshots

Additional Notes

• Styling has been updated to include a cursor pointer on hover to indicate draggable elements.
• Efforts were made to reduce border thickness and fix outline styles for a cleaner UI appearance during drag and drop operations.
• Code has been linted and reworked for better performance and readability.

[mboynes]

💯. Reviewed and tested, works great!