Make monaco-editor use monaco-editor-core and friends

[remcohaszing]

Recently I created a pull request for monaco-yaml to use Monaco imports instead of the global Monaco object (remcohaszing/monaco-yaml#48).

To implement this, I had to make a choice: should monaco-yaml support monaco-editor or monaco-editor-core?

I don’t think Monaco plugins should have to make this choice. I think monaco-editor should become a simple package that uses monaco-editor-core, monaco-json, monaco-css, monaco-html, and monaco-typescript as regular dependencies instead of bundling them. This gives third party plugins to create an implementation based on monaco-editor-core that also works for monaco-editor.