Fix itchio:// support on all platforms (regression introduced by object payload for OPEN_URL)
Fix itchio:// support on all platforms (regression introduced by object payload for OPEN_URL)

itchio/itch,itchio/itch,itchio/itch,itchio/itch,itchio/itchio-app,leafo/itchio-app,itchio/itchio-app,itchio/itchio-app,itchio/itch,leafo/itchio-app,itchio/itch,leafo/itchio-app