Create accessible external links

[joemull]

Fixes #306.

This strategy uses a JS script on all pages to apply the proper attributes and icon.

Why JS is needed

I wonder whether it would be cleaner to do this just in the CSS without needing any JS, with a target for any links which have other domains?
a[href^="http"]:after

It's not possible to meet all the user requirements with CSS only, since we need to add the blank target attribute to user-generated content like news items, and we also want to check that urls do not include the current domain (there are sometimes hard-coded links to the openlibhums website that include the domain).

Screenshots

[StephDriver]

• I like the svg solution - especially compared with the use of fonts on Janeway.

• I think the spacing isn't quite right everywhere:

• I would like you to consider the readability impact of these icons. When adding similar to the Janeway front of house the text was cluttered, so I made them smaller, recede and in superscript so that they don't clutter the text as much. I'm not saying exactly the same is needed here, I offer this as a starting point for considering ways to keep the text readable.

opacity = 70%
vertical-align: super
font-size: 0.7em

versus