Add time format example to the description of commands that use TimeSpan. (#267)

This PR was made to help users who are trying /remind for the first time
by showing an example of the correct time format in the description.

---------

Signed-off-by: Macintxsh <95250141+mctaylors@users.noreply.github.com>
Signed-off-by: mctaylors <cantsendmails@mctaylors.ru>

src/Commands/ToolsCommandGroup.cs

@@ -461,6 +461,7 @@ public class ToolsCommandGroup : CommandGroup
         {
             var failedEmbed = new EmbedBuilder()
                 .WithSmallTitle(Messages.InvalidTimeSpan, bot)
+                .WithDescription(Messages.TimeSpanExample)
                 .WithColour(ColorsList.Red)
                 .Build();