update color theme in demo.

save current theme preference to localstorage.
update to v0.10.0.

public/demo/theme-toggle.js

@@ -8,6 +8,11 @@ document.addEventListener("DOMContentLoaded", () => {
 
 	toggle.addEventListener("click", () => {
 		document.body.classList.toggle("invertedTheme");
+
+		localStorage.setItem(
+			"useInvertedTheme",
+			document.body.classList.contains("invertedTheme") ? "true" : "",
+		);
 	});
 
 	toggle.innerHTML = `
@@ -28,6 +33,9 @@ document.addEventListener("DOMContentLoaded", () => {
     `.trim();
 
 	document.body.appendChild(toggle);
+
+	if (!!localStorage.getItem("useInvertedTheme"))
+		document.body.classList.add("invertedTheme");
 });
 
 // @license-end