Eclipse is great, but Java is different platform than Node.js. While Eclipse Runtime has a lot of architectural solution and features, it is huge to develop quickly and understand.
There are Node.js based IDEs that run in a browser, like Scripted.
First step would be light Eclipse component JSContainer, that just uses WebView. For whole IDE to work all these component hierarchies should have shared property base_address, that is address of web server. In this way, there can be easy switch from locally running web-server to some LAN or cloud server.
Examples of tools we could use
In-browser Markdown Editor http://benweet.github.io/stackedit/