v0.3.0

• Added an Element block, allowing custom structured data to be added to the JSON content via XML-like syntax;
• Added title and meta attributes to the Code block;
• Added an MDX extension, defining a custom transformer with support for frontmatter and MDX block elements;
• Updated CORS to allow API access from the browser;
• Extended /search endpoint to return content piece metadata;
• Redesigned editor menus for Image, Embed, and Code blocks.
• Restructured @vrite/backend package;
• Removed the Wrapper block (replaced by Element);
• Removed CORS image proxy;