Update engine

[slimbuck]

And also:

• small build updates
• construct png encoder on demand

[Copilot]

Pull Request Overview

This PR updates project dependencies and implements lazy loading for the PNG exporter while making some build configuration improvements.

• Updates various npm dependencies to their latest versions
• Implements on-demand construction of the PNG exporter to improve initialization performance
• Simplifies build configuration by removing unused variables and streamlining TypeScript compiler options

Reviewed Changes

Copilot reviewed 4 out of 5 changed files in this pull request and generated 1 comment.

File	Description
src/viewer.ts	Removes eager PNG exporter initialization and implements lazy loading in downloadPngScreenshot method; adds 'sog' file extension support
src/png-exporter.ts	Improves async handling by moving lodepng initialization outside the message handler
rollup.config.mjs	Simplifies build configuration by consolidating engine path logic and removing unused PCUI variables
package.json	Updates multiple dependencies to latest versions including TypeScript, ESLint, and PlayCanvas

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