Add Keys.TELEPORT_DURATION for DisplayEntity

Closes #2508

Author: DrZoddiak

src/main/java/org/spongepowered/api/data/Keys.java

@@ -3113,6 +3113,11 @@ public final class Keys {
      */
     public static final Key<Value<Vector3i>> TARGET_POSITION = Keys.key(ResourceKey.sponge("target_position"), Vector3i.class);
 
+    /**
+     * The teleport duration of a {@link DisplayEntity}
+     */
+    public static final Key<Value<Ticks>> TELEPORT_DURATION = Keys.key(ResourceKey.sponge("teleport_duration"), Ticks.class);
+
     /**
      * The {@link TemperatureModifier} of a {@link Biome}.
      * Readonly

src/main/java/org/spongepowered/api/entity/display/DisplayEntity.java

@@ -64,6 +64,15 @@ default Ticks interpolationDelay() {
         return this.require(Keys.INTERPOLATION_DELAY);
     }
 
+    /**
+     * Returns the duration of the teleportation
+     *
+     * @return the duration of the teleportation
+     */
+    default Ticks teleportDuration() {
+        return this.require(Keys.TELEPORT_DURATION);
+    }
+
     default BillboardType billboardType() {
         return this.require(Keys.BILLBOARD_TYPE);
     }