monaco-editor-auto-typings is a plugin for Microsoft's Monaco Editor, which automatically loads type declarations when you enter import-calls in the code editor.
Try it out in the demo on the left! Add some imports to some libraries available on npm, such as import express from 'express';, and see that any imported variables are automatically strictly typed.
monaco-editor-auto-typings comes with lots of customization options, but is still a one-liner to add to your project. It works by loading declarations from UnPkg. They can then be optionally cached in localStorage or elsewhere.
Check out the code example and setup instructions on Github. You can also find the code that powers this exact page here. Developed and maintained by Lukas Bach.