The plugin adds a code editor view to Obsidian. The code editor uses the powerful Monaco Editor, which also powers VS Code.
Caveat: This plugin currently relies on hosted dependencies and thus needs an internet connection. Read below for more information.
In the plugin settings, you can configure for which file extensions the editor will be available as default editor. You can also create new code files, either by right clicking on a folder in the side pane and clicking on "Create Code File", search for "Create new Code File" in the command palette or by using the "Create Code File" button in the ribbon.
Due to the complicated nature of bundling the Monaco Editor, the plugin currently relies on a hosted version of the editor. This means that the plugin needs an internet connection to work, and has a dependency on the hosted editor, which is currently available on https://embeddable-monaco.lukasbach.com.
I hope to remove this dependency in the future, but this was the easiest way to get the plugin to work for now.