Add a class to interlanguage links

The <li> elements in the interlanguage links list are not necessarily
links to other languages. They may also be links to Wikidata,
for example.

This commit adds a class that identifies the actual links as such.

Bug: 56819
Change-Id: Ia995f89504d19ac281d55e0c19c51c9dc6442d8e
Merge "Add a class to interlanguage links"