Closes #129

Exposing node and mark objects to be accessible via nodes and marks resolver functions. This adds possibility to access the whole rich text node, including type, attrs, and most importantly, content data, allowing more advanced configuration possibilities.

Especially useful when the component supports data passing via props only, and do not support <slot /> to pass the data as children, f.e. https://docs.astro.build/en/reference/api-reference/#code-

The PR makes it possible to configure such components with RichTextRenderer.

Changes

• Expose the possibility to access content inside schema resolvers
• Remove custom CodeBlock component in favour of native Astro Code component
• Add Heading component which is has no slots, thus data is via props only as an example
• Cover with unit tests