Expose ignoreSelection in gamemain.lua

[4z0t]

Description of the proposed changes

Allow mods read ignoreSelection with no hooking.

Checklist

• [x] Changes are annotated, including comments where useful
• [ ] Changes are documented in a changelog snippet according to the guidelines.
• [x] Request 2-3 reviewers from the list of reviewers and their areas of knowledge.

Summary by CodeRabbit

• Refactor
  • Internal code improvements to enhance maintainability and code organization.

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