Add pictograms

[simongray]

Based on my feedback session with Francis Bond I'd like to see if we can find the time to add pictograms to DanNet. These are non-commercial share-alike (or something like that) and the dataset is readily available at: https://arasaac.org/

[simongray]

• The pictograms themselves are available via the ARASAAC public REST API (api.arasaac.org), with images served from a static CDN (static.arasaac.org/pictograms/{id}/...).
• There's no bulk "dataset" download on the website itself, just per-pictogram metadata plus constructed image URLs. Since we only want to display pictograms when available rather than redistribute them, the CC BY-NC-SA license is much less of a concern as we'd just be hotlinking/displaying with attribution, not editing or republishing the data.
• For the synset linkage: the relevant resource is Arasaac-WN (Schwab et al., LREC 2020), which links ARASAAC pictograms to Princeton WordNet synsets, not CILI or OEWN directly. It's a curated set of roughly 800 pictograms mapped to PWN synsets (so coverage is sparse relative to ARASAAC's ~12k+ pictograms).
• Because the links are anchored to PWN sense keys/offsets, they're one hop from CILI/OEWN and therefore bridgeable to DanNet via our existing ILI linkage: DanNet synset → ILI/PWN → Arasaac-WN → pictogram ID → image.

The main open questions before building anything are (a) which PWN version Arasaac-WN uses and whether it aligns with our CILI mapping, and (b) accepting that the feature will only light up for a small fraction of synsets.