Add CodeMash QCon and Scala Days conference data

[Gwani-28]

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

Summary

• Add CodeMash, QCon, and Scala Days to the conference dataset table.
• Preserve the existing six-column README schema.
• Use public source material and conservative values where no public Speaker Engagement Agreement commitment was found.

Source notes

• CodeMash conference/about: https://codemash.org/ and https://codemash.org/About/
• CodeMash 2026 Sessionize CFP: https://sessionize.com/codemash-2026/
• QCon conference series: https://qconferences.com/
• C4Media organizer/company page: https://c4media.com/
• QCon speaker support: https://qconsf.com/qcon-cares
• Scala Days site: https://scaladays.org/
• Scala Days 2026 announcement and organizer partnership: https://www.scala-lang.org/blog/2026/03/26/scala-days-2026.html
• Scala Days 2026 CFP: https://cfp.scaladays.org/scala26/cfp

Data choices

• CodeMash: SEA No; free ticket Yes; reimbursement Partial from speaker-benefit CFP material; compensation Workshops following the workshop/PreCompiler speaker-benefit category.
• QCon: SEA No; free ticket Yes; reimbursement Partial because QCon documents travel/accommodation support; compensation Never because I did not find a public speaker-fee commitment.
• Scala Days: SEA No; free ticket No; reimbursement No; compensation Never because I did not find public speaker benefit, reimbursement, or honorarium commitments.

Validation

• git diff --check
• README table validation: 14 conference data rows, all with 6 columns.
• Official source URLs checked for successful responses before submission.

AI-assisted implementation, manually source-checked and reviewed before submission.

[Gwani-28]

Submitted PR #372 for the combined conference-data bounties #4/#10/#11. It adds CodeMash, QCon, and Scala Days with public source notes in the PR body and validation completed (git diff --check, README six-column table check).