fix(export): enable proper file downloads and fix empty PNG export

src/scripts/ascii-exporter.ts

@@ -8,6 +8,15 @@ export class AsciiExporter {
         link.click();
     }
 
+    static downloadText(content: string, filename: string) {
+        const blob = new Blob([content], { type: 'text/plain;charset=utf-8' });
+        const link = document.createElement('a');
+        link.href = URL.createObjectURL(blob);
+        link.download = filename;
+        link.click();
+        URL.revokeObjectURL(link.href);
+    }
+
     static async copyToClipboard(text: string): Promise<void> {
         if (navigator.clipboard && navigator.clipboard.writeText) {
             await navigator.clipboard.writeText(text);