Update _config.yml

_config.yml

@@ -16,6 +16,7 @@ header_pages:
 #      - events/language-and-vision-workshop/language-and-vision-workshop.md
 #      - events/ethics-for-nlp/ethics-for-nlp.md
 #      - events/out-to-the-islands/out-to-the-islands.md
+#      - events/positronic-brain/positronic-brain.md
   - path: projects.md
 #    sub_pages:
 #      - projects/utopia/cc.md