Set ts compiler to strict, refactored a bit

src/utils/dom.ts

@@ -0,0 +1,9 @@
+/**
+ * Get an element by id
+ * @param id The id of the element
+ * @type T The type of the HTMLElement
+ * @returns The element with the given id, or null if it doesn't exist
+ */
+export function getElementById<T extends HTMLElement = HTMLElement>(id: string): T | null {
+    return document.getElementById(id) as T | null;
+}