Add PCD @ Linz to the PCD map

[github-actions]

Note

The Plus Code was auto-recovered from the user's input (875M+VP Linz, Austria) using the city as a reference. Please verify the map pin placement is correct (https://plus.codes/8FWP875M+VP).

Closes #27

This PR was generated from the "New Event" issue form for PCD @ Linz.
Submitted by @SableRaf.

Review checklist:

• Event name "PCD @ Linz" is correct
• Public name "Raphaël de Courville" and email "raphael@processing.org" are correct
• Date is correct; time is marked TBD — confirm this is intentional
• Location is marked TBD — confirm this is intentional
• Check the map and event details page in the Netlify preview (link posted below by the Netlify bot)

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