Fix dark scheme detect function

Update `isInitialThemeDark` so that any value loaded from local-storage
takes precedence. Prior to this commit, if the browser preferred the
dark theme then the saved light theme would never be restored.

See gh-23

Author: jk-tagbangers

src/main/js/setup/switchtheme.js

@@ -21,9 +21,6 @@
 
   const localStorage = window.localStorage;
   const htmlElement = document.documentElement;
-  const prefersDarkColorScheme = window.matchMedia(
-    "(prefers-color-scheme: dark)"
-  );
 
   swithInitialTheme();
   window.addEventListener("load", onWindowLoad);
@@ -46,7 +43,18 @@
   }
 
   function isInitialThemeDark() {
-    return loadTheme() === "dark" || prefersDarkColorScheme.matches;
+    const prefersDarkColorScheme = window.matchMedia(
+      "(prefers-color-scheme: dark)"
+    );
+    const savedColorScheme = loadTheme();
+    switch (savedColorScheme) {
+      case "dark":
+        return true;
+      case "light":
+        return false;
+      default:
+        return prefersDarkColorScheme.matches;
+    }
   }
 
   function onThemeChange() {