Add bitcoin++ payments edition for opensource

[confs-tech-bot]

Conference information

Website: https://btcpp.dev/berlin26
CFP: https://btcpp.dev/talk/berlin26

Github: @niftynei
Twitter: https://twitter.com/@btcplusplus

// opensource

{
  "name": "bitcoin++ payments edition",
  "url": "https://btcpp.dev/berlin26",
  "startDate": "2026-10-01",
  "endDate": "2026-10-03",
  "city": "Berlin",
  "country": "Germany",
  "online": false,
  "locales": "EN",
  "cfpUrl": "https://btcpp.dev/talk/berlin26",
  "cfpEndDate": "2026-08-17",
  "twitter": "@btcplusplus"
}