Packaging an html template, javascript and css to be consumed by multiple platforms

I have a large rails application that I am wanting to split out into smaller applications. The one piece of this application that will be universal to all smaller applications is the mast and footer. I would like to extract the html, javascript and css for the mast and footer into it's own package that each app can load and render.

The main issue I'm running into is that the apps will likely not all be written in rails. Some will be rails, some will be expressjs, some written in Go, and some may end up being written in other languages, so my solution needs to be language agnostic.

My thought is that I can extract the html, css and javascript into it's own git repo, use mustache templates for the html, and then use grunt or a similar build tool to build a gem, a package.json structure and a golang module. Possibly each in it's own git submodule.

I'm curious if there is a more standardized way of doing this. Or if anyone knows of a simpler way of achieving this goal.

Sounds like the technology in common is HTML/JS/CSS.

Wouldn't it be better to export the mast and footer as a self contained JS library, or more precisely, as widgets?

So whatever the application server tech stack would be, you could always generate the HTML in the form of:

<script src="your_widgets.js"></script>
<script>new Footer.render('id_of_dom_element_to_render_to');</script>

By doing so, whether you want the widget library to load the template or you want to embed the template into the widget library or whether you want to simply just construct it using HTMLFragment will not be limited by the server tech choice.