Building iife and CommonJS

Well, ES6 modules can't be imported unless you are serving files on a HTTP server so this version includes builds in different formats so it can be used under file:// protocol. Shame on you ES6 modules.

• Add custom elements polyfill as dependency
• Add rollup as dependency and export cjs and iife versions
• Example of build able to run from filesystem

Breaking changes

• "Raw repl" and file operations return promises.
• Switch callbacks for events on connection opening, authentication and incoming messages.
• Examples using Custom Elements (v1) to create an interactive prompt, file manager and run code from a text editor.
• Adds optional interval between lines of code on execFromString necessary for the ESP32 implementation of the WebREPL protocol.
• WebREPL class documentation generated with JSDoc.
• Some tests (I promise I did my best)

Initial release

This release contains everything needed for performing the basic WebREPL operations (and a little bit more ;B)