implemented save file compression in browser

src/lib/formatBytes.ts

@@ -0,0 +1,11 @@
+const KILOBYTE = 1024
+const MEGABYTE = 1024 * KILOBYTE
+
+/**
+ * Formats a byte count for error messages and status lines, e.g. "12.3 MB".
+ */
+export function formatBytes(bytes: number): string {
+    if (bytes >= MEGABYTE) return `${(bytes / MEGABYTE).toFixed(1)} MB`
+    if (bytes >= KILOBYTE) return `${(bytes / KILOBYTE).toFixed(1)} KB`
+    return `${bytes} B`
+}