Move styles into code

ts/document.ts

@@ -0,0 +1,19 @@
+export function whenLoaded(callback: () => void) {
+    if (document.readyState === "loading") {
+        document.addEventListener("DOMContentLoaded", callback);
+    } else {
+        callback();
+    }
+}
+
+export function addStyle(style: string) {
+    whenLoaded(() => {
+        addStyleNow(style);
+    });
+}
+
+export function addStyleNow(style: string) {
+    const sheet = new CSSStyleSheet();
+    sheet.replaceSync(style);
+    document.adoptedStyleSheets = [...document.adoptedStyleSheets, sheet];
+}