AK: Add human_readable_digital_time() helper

Converts seconds into a readable digital format. For example:
30 seconds	= "00:30"
90 seconds	= "01:30"
86401 seconds	= "24:00:01"
And so on.

AK/NumberFormat.h

@@ -63,8 +63,27 @@ static inline String human_readable_time(i64 time_in_seconds)
     return builder.to_string();
 }
 
+static inline String human_readable_digital_time(i64 time_in_seconds)
+{
+    auto hours = time_in_seconds / 3600;
+    time_in_seconds = time_in_seconds % 3600;
+
+    auto minutes = time_in_seconds / 60;
+    time_in_seconds = time_in_seconds % 60;
+
+    StringBuilder builder;
+
+    if (hours > 0)
+        builder.appendff("{:02}:", hours);
+    builder.appendff("{:02}:", minutes);
+    builder.appendff("{:02}", time_in_seconds);
+
+    return builder.to_string();
+}
+
 }
 
+using AK::human_readable_digital_time;
 using AK::human_readable_size;
 using AK::human_readable_size_long;
 using AK::human_readable_time;