Alternative: cpiber/epub-gen-memory for both node and browser

[cpiber]

Since this repo appears to be dead, here's a shameless plug for my own fork cpiber/epub-gen-memory.

A few major differences:

• Rewritten in TypeScript, with modern libraries and async/await
• Supports running in the browser
• No direct file-system access
• Minor changes in the API
• Fix some EPUB issues (validated using http://validator.idpf.org/)

I hope some of you can use that, and I'm always open for PRs!