Add Scala Days, CodeMash, and QCon data

[Yassinbrine]

Summary

• add Scala Days, CodeMash, and QCon to the conference tracking table
• preserve the existing README table schema and current row style
• use conservative public-source values where I did not find a public SEA or speaker-fee commitment

/claim #4
/claim #10
/claim #11

Source notes

• Scala Days official site: https://scaladays.org/
• Scala Days organizer/source note: https://www.scala-lang.org/blog/2026/03/26/scala-days-2026.html
• CodeMash official site: https://codemash.org/
• CodeMash organizer page: https://codemash.org/organizers/
• CodeMash speaker-benefits source: https://codemash.org/call-for-speakers-announcement/
• QCon official site: https://qconferences.com/
• C4Media organizer/company site: https://c4media.com/
• InfoQ QCon speaker-support reference: https://www.infoq.com/articles/guide-curating-technical-conference-track/

Data choices

• No for SEA where I did not find a public commitment that the organizer signs the Speaker Engagement Agreement.
• Partial for CodeMash reimbursement because public speaker benefits mention hotel/housing support but not full travel/per diem coverage.
• PreCompilers for CodeMash compensation because the public benefits source describes a PreCompiler workshop honorarium.
• Partial for QCon reimbursement because the public speaker-support reference mentions travel/accommodation support, but I did not find a full per diem/general expense policy.
• Never for QCon and Scala Days compensation because I did not find a public speaker-fee or honorarium commitment.

Validation

• git diff --check
• README table check: all 14 conference rows have 7 pipe separators
• source-link HTTP checks returned 200 for Scala Days, Scala Days source note, CodeMash, CodeMash organizers, CodeMash speaker benefits, QCon, C4Media, and InfoQ speaker-support reference

Demo

This is a static README data update, so the PR diff is the review/demo surface.