fix typings so they are usable for building the project itself

src/main/resources/lib/globals/set.d.ts

@@ -0,0 +1,18 @@
+interface Set<V> {
+	readonly size: number;
+	add(val: V): this;
+	has(key: V): boolean;
+	delete(key: V): boolean;
+	clear(): void;
+
+	keys(): V[];
+	values(): V[];
+	entries(): [V, V][];
+
+	forEach(cb: (val: V, key: V, map: this) => void, self?: any): void;
+
+	[Symbol.iterator](): Iterator<V>;
+}
+interface SetConstructor {
+	new <V>(iterable?: Iterable<V>): Set<V>;
+}