libjs-cssrelpreload - 3.1.0+dfsg+~cs3.1.3-1 main

This JavaScript library provides functions to load CSS asynchronously.
.
Referencing CSS stylesheets with link[rel=stylesheet] or @import causes
browsers to delay page rendering while a stylesheet loads. When loading
stylesheets that are not critical to the initial rendering of a page, this
blocking behavior is undesirable. The new standard
enables loading stylesheets asynchronously, without blocking rendering, and
loadCSS provides a JavaScript polyfill for that feature to allow it to work
across browsers, as well as providing its own JavaScript method for loading
stylesheets.