Show test characters in underline test

demo/client.ts

@@ -766,12 +766,23 @@ function underlineTest() {
   term.write('\n\n\r');
   term.writeln('Underline styles:');
   term.writeln('');
-  term.writeln(`${u(0)}4:0m - No underline`);
-  term.writeln(`${u(1)}4:1m - Straight`);
-  term.writeln(`${u(2)}4:2m - Double`);
-  term.writeln(`${u(3)}4:3m - Curly`);
-  term.writeln(`${u(4)}4:4m - Dotted`);
-  term.writeln(`${u(5)}4:5m - Dashed\x1b[0m`);
+  function showSequence(id: number, name: string) {
+    let alphabet = '';
+    for (let i = 97; i < 123; i++) {
+      alphabet += String.fromCharCode(i);
+    }
+    let numbers = '';
+    for (let i = 0; i < 10; i++) {
+      numbers += i.toString();
+    }
+    return `${u(id)}4:${id}m - ${name}\x1b[4:0m`.padEnd(33, ' ') + `${u(id)}${alphabet} ${numbers}\x1b[4:0m`;
+  }
+  term.writeln(showSequence(0, 'No underline'));
+  term.writeln(showSequence(1, 'Straight'));
+  term.writeln(showSequence(2, 'Double'));
+  term.writeln(showSequence(3, 'Curly'));
+  term.writeln(showSequence(4, 'Dotted'));
+  term.writeln(showSequence(5, 'Dashed'));
   term.writeln('');
   term.writeln(`Underline colors (256 color mode):`);
   term.writeln('');