interventions: document language of anchor text about derrida-django

[rlskoeser]

Note that we only need to support a single language for each of these.

[kac3]

Hi @bwhicks @rlskoeser, I see where I can document the language of the anchor text -- but not where I can document the anchor text itself! If that's because I neglected to create a user story, my apologies. We need a field for anchor text (in the image below, "guerres civiles") distinct from annotation text.

[rlskoeser]

Whoops! I thought about that in passing at some point (I wondered why we were only documenting the language of the anchor text) but failed to ask. Let's add a new story for anchor text, I think we can add it fairly quickly.

[rlskoeser]

See #70 for anchor text.