Adds ignore rules for specific deps in dependabot config

[Jwaegebaert]

Configure Dependabot to ignore:

• @actions packages v3.x - These are pure ESM modules incompatible with @vercel/ncc bundler
• @types/node - Should be updated manually to match GitHub Actions runtime

This prevents build failures like the one in #22 where v3.x @actions packages caused module resolution errors during the ncc build step.

[Copilot]

Pull request overview

This PR configures Dependabot to prevent automatic dependency updates that would break the build. It addresses the issue from PR #22 where v3.x @actions packages (pure ESM modules) caused build failures with the @vercel/ncc bundler.

Changes:

• Added ignore rules for @actions/core, @actions/exec, and @actions/io to block major version updates to v3.x
• Added ignore rule for @types/node to require manual updates aligned with the node24 runtime

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