This is great! This will make bootstrap more attractive and competitive as a framework.
JQuery was one of the most important frameworks in Javascript history. It has enabled us to built real webapps. However since then differences between browsers shrunk significantly and we learned how to build maintainable and scalable apps in a more declarative fashion (hello React, Angular and friends)
I am still more fond of jQuery's ajax functionality than anything that followed, including the fetch API.
I've always liked to use axios which provides a jQuery-ish AJAX library. Works in the browser and server-side with NodeJS.
https://github.com/axios/axios
Much nicer to use than fetch IMHO