Desktop: Load themes as CSS variables for use in custom themes and internal components

packages/lib/hooks/useAsyncEffect.ts

@@ -0,0 +1,18 @@
+import shim from '../shim';
+const { useEffect } = shim.react();
+
+export interface AsyncEffectEvent {
+	cancelled: boolean;
+}
+
+export type EffectFunction = (event: AsyncEffectEvent)=> Promise<void>;
+
+export default function(effect: EffectFunction, dependencies: any[]) {
+	useEffect(() => {
+		const event: AsyncEffectEvent = { cancelled: false };
+		void effect(event);
+		return () => {
+			event.cancelled = true;
+		};
+	}, dependencies);
+}