frontend: drop dependencies to orphaned javascript packages
First, let's clarify what those packages are, `js-html5shiv`:
> The HTML5 Shiv enables use of HTML5 sectioning elements in legacy Internet
> Explorer and provides basic HTML5 styling for Internet Explorer 6-9, Safari 4.x
> (and iPhone 3.x), and Firefox 3.x.
And `js-respond`:
> The goal of this script is to provide a fast and lightweight (3kb minified /
> 1kb gzipped) script to enable responsive web designs in browsers that don't
> support CSS3 Media Queries - in particular, Internet Explorer 8 and under.
> It's written in such a way that it will probably patch support for other
> non-supporting browsers as well.
Internet Explorer 8 is now dead for a couple of years
> Effective January 12, 2016, Internet Explorer 8 is no longer
> supported on any client or server version of Windows, due to new
> policies specifying that only the newest version of IE available
> for a supported version of Windows will be supported. By
> January 16, 2018, Microsoft has ended support for IE8.
I didn't find the official reason why those packages got orphaned but
I persume that it is because nobody longer cares about IE8. IMHO we
can safely drop the code instead of maintaining those packages by ourselves.