We have published a new npm module that let's you convert Markdown and HTML into Storyblok's Richtext field format.

Check it out here: https://github.com/storyblok/storyblok-markdown-richtext

There is also an example of how to use it with our migration CLI to transform fields: https://github.com/storyblok/storyblok#2-transform-a-markdown-field-into-a-richtext-field