Add CodeMash conference data

[GoodMorC]

Adds CodeMash to the conference tracker.

/claim #10

Source notes:

• CodeMash public site used for the conference and organizer link: https://codemash.org/
• CodeMash speaker-benefits information indicates speakers receive conference admission, with hotel/travel support handled as a limited benefit rather than full reimbursement, and workshop/precompiler compensation rather than general session compensation.
• I did not find a public statement that CodeMash is willing to sign the Speaker Engagement Agreement, so the SEA value is conservatively set to No per the issue guidance.

Validation:

• Markdown table column-count check passed
• git diff --check passed

Fixes #10