Add: Through load speed limit setting

src/lang/english.txt

@@ -1366,6 +1366,10 @@ STR_CONFIG_SETTING_PERCENTAGE                                   :{COMMA}%
 STR_CONFIG_SETTING_ROAD_VEHICLE_SLOPE_STEEPNESS                 :Slope steepness for road vehicles: {STRING2}
 STR_CONFIG_SETTING_ROAD_VEHICLE_SLOPE_STEEPNESS_HELPTEXT        :Steepness of a sloped tile for a road vehicle. Higher values make it more difficult to climb a hill
 
+STR_CONFIG_SETTING_THROUGH_LOAD_SPEED_LIMIT                     :Through load maximum speed: {STRING2}
+STR_CONFIG_SETTING_THROUGH_LOAD_SPEED_LIMIT_HELPTEXT            :The maximum allowable speed for through load trains
+STR_CONFIG_SETTING_THROUGH_LOAD_SPEED_LIMIT_VAL                 :{VELOCITY}
+
 STR_CONFIG_SETTING_FORBID_90_DEG                                :Forbid trains from making 90° turns: {STRING2}
 STR_CONFIG_SETTING_FORBID_90_DEG_HELPTEXT                       :90 degree turns occur when a horizontal track is directly followed by a vertical track piece on the adjacent tile, thus making the train turn by 90 degree when traversing the tile edge instead of the usual 45 degrees for other track combinations.
 STR_CONFIG_SETTING_BACK_ONE_WAY_PBS_SAFE_WAITING                :Pathfind up to back of one-way path signals: {STRING2}