ReadMe has pre-built widgets for you to use, that you can drag and drop on the right side of the content editor.
The header widget will create an h1 header for you.
The code sample widget allows you to write styled code samples, and you should be able to add as many tabs as you need for different languages.
The callout widget can be used to display different callouts to give your users warnings or cautions.
Use this widget to create a table such as this:
Column Title 1
Column Title 2
Use this widget to upload an image and choose how you want to scale it.
Here you can try embedding YouTube, Github Gists, JSFiddles, PDFs and more
Lastly you can add custom HTML/CSS for your content using this widget if you need anything else!