feat(conferences): add Warsaw Python Pizza 2026 entry (#297)

Author: piotrgredowski

2026.csv

@@ -5,6 +5,7 @@ PythonAsia,2026-03-21,2026-03-23,"Malate, Manila",PHL,De La Salle University Man
 PyCon Lithuania,2026-04-08,2026-04-10,"Vilnius, Lithuania",LTU,TASKIUS Art & Science School,,2026-01-15,https://pycon.lt/2026,https://pycon.lt/2026/call-for-proposals,https://pycon.lt/2026/partnership
 PyCon DE & PyData,2026-04-13,2026-04-17,"Darmstadt, Germany",DEU,darmstadtium,2026-01-11,2026-01-11,https://pycon.de,https://2026.pycon.de/call-for-proposals/,https://2026.pycon.de/sponsoring/
 PyTexas,2026-04-17,2026-04-19,"Austin, Texas United States",USA,Austin Central Library,,2025-12-07,https://www.pytexas.org/2026/,https://pretalx.com/pytexas-2026/,https://www.pytexas.org/2026/sponsors/sponsor-us/
+Warsaw Python Pizza,2026-05-09,2026-05-09,"Warsaw, Poland",POL,"PJAIT building A, Koszykowa 86",,2026-04-12,https://warsaw.python.pizza,https://forms.gle/5pqj68ES9ENaGPBf6,https://warsaw.python.pizza/#sponsors
 PyCon US,2026-05-13,2026-05-19,"Long Beach, California, United States of America",USA,Long Beach Convention and Entertainment Center,,2025-12-19,https://us.pycon.org/2026/,https://us.pycon.org/2026/speaking/guidelines/,https://us.pycon.org/2026/sponsorship/why-sponsor/
 PyCon Italia,2026-05-27,2026-05-30,"Bologna, Italy",ITA,Savoia Hotel Regency,,,https://2026.pycon.it,,https://2026.pycon.it/sponsor/
 EuroPython,2026-07-13,2026-07-19,"Kraków, Poland",POL,ICE Kraków Congress Centre,2026-02-15,2026-02-15,https://ep2026.europython.eu,https://ep2026.europython.eu/cfp,https://ep2026.europython.eu/sponsors