Using NODE_ENV to determine if frontend code should be included in the build.

Made use of const values to store global data.
Polling is done on every tick, supposedly it's the best approach for libretro.

Fixes issue with zip file handling.

Making use of the newly added `buildRomData()` method.

Making use of the newly added `buildRomData()` method.

Handling of GameShark RAM banks differently.
Added parsing integer value errors.

This has been moved to emukit.

Uses js-sys to interact with the Javascript VM, to obtain Date() reference.

Makes use of the most recent save state support in EmuKit.
Thumbnail image support.