Track icon

Getting in early with the important stuff - which logo do we want to use for the `dyalog-apl` track? I can see a case for both of these:

- the "official" APL logo https://aplwiki.com/images/c/c6/APL_logo.png

- the Dyalog APL logo http://aplwiki.com/images/d/df/Dyalog_icon.png

---

I'm not sure if other variants would be added to Exercism once this one is live. In terms of recognition as 'APL' I'd lean towards the official one, but the Dyalog one is more specific.

Review the two candidate APL logo assets linked in the issue and determine which should represent the dyalog-apl track. The issue does not name a file, test, or implementation entry point; done requires a maintainer decision and updating the track branding with the selected logo.

Written by the indexing model from the issue text.