Add CfP deadline and sponsorship link for PyCon US 2026 (#139)

* Update CFP and add sponsorship link for PyCon US 2026

* fix: cfp formatting

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Co-authored-by: Jesper Dramsch <[email protected]>

Author: egeakman

_data/conferences.yml

@@ -560,10 +560,12 @@
 - conference: PyCon US
   year: 2026
   link: https://us.pycon.org/2026/
-  cfp: TBA
+  cfp_link: https://us.pycon.org/2026/speaking/talks/
+  cfp: "2025-12-19 23:59:00"
   place: Long Beach, USA
   start: 2026-05-13
   end: 2026-05-19
+  sponsor: https://us.pycon.org/2026/sponsorship/why-sponsor/
   mastodon: https://fosstodon.org/@pycon
   sub: PY
   location: