fix: remove global in favor of globalThis for better compatibility

[natew]

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Motivation

I'm using react-navigation with Vite (browser-loaded esm) and this is actually really tricky to fix because imports are always hoisted above code, so my polyfill attempts get pushed below the react-navigation import unless I literally add a script tag above the app entrypoint.

Moving to globalThis should be safe and supported in most node/react-native/browsers from the last few years.

Test plan

I haven't tested thoroughly.

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