embed the previously manually edited outdated documentation

from https://github.com/OpenRA/OpenRA/wiki/Trait-Documentation

OpenRA.Mods.RA/Buildings/RepairableBuilding.cs

@@ -11,9 +11,11 @@
 using System;
 using OpenRA.Mods.RA.Effects;
 using OpenRA.Traits;
+using OpenRA.FileFormats;
 
 namespace OpenRA.Mods.RA.Buildings
 {
+	[Desc("Building can be repaired by the repair button.")]
 	public class RepairableBuildingInfo : ITraitInfo, Requires<HealthInfo>
 	{
 		public readonly int RepairPercent = 20;