Check relative link handling in webviews #11

In the dumps, links within the same language's wiki are written as relative
links (./Article_Title), while cross-wiki links (e.g. [[:fr:Pomme]]) are
already expanded to absolute links (https://fr.wikipedia.org/wiki/Pomme).
See https://en.wikipedia.org/wiki/Help:Interwiki_linking for more examples of wikitext linking.

The dump html includes a base element set to //lang.wikipedia.org/wiki/, but when opened as a file in firefox it assumes the scheme is file: so they don't work.

We should see if the android/ios webviews have a similar problem, and if so updating the html processing to set the scheme in the base element should handle it.

Discussed more in #10.