When writing code you have to create documentation to give the user starting point. Documentation in the code repository needs to be in markdown format, and even several documentation websites such as Docusaurus allow you to create blogs and pages in Markdown format.
The markdown file extension is .md and documents need to be written in a specific format like for H1 it should be written with # and for H2 it should be ## and H3 should be ### etc.
You can refer to GitHub Doc to learn more about how to write markdown documents.
In this blog, you will find a list of an offline and online tool that converts Word documents to Markdown documents.