Merge pull request phaserjs#5285 from samme/feature/arcade-config-fixedstep

Add ArcadeWorldConfig.fixedStep

Author: photonstorm

src/physics/arcade/World.js

@@ -165,7 +165,7 @@ var World = new Class({
          * @default true
          * @since 3.23.0
          */
-        this.fixedStep = true;
+        this.fixedStep = GetValue(config, 'fixedStep', true);
 
         /**
          * The amount of elapsed ms since the last frame.

src/physics/arcade/typedefs/ArcadeWorldConfig.js

@@ -3,6 +3,7 @@
  * @since 3.0.0
  *
  * @property {number} [fps=60] - Sets {@link Phaser.Physics.Arcade.World#fps}.
+ * @property {boolean} [fixedStep=true] - Sets {@link Phaser.Physics.Arcade.World#fixedStep}.
  * @property {number} [timeScale=1] - Sets {@link Phaser.Physics.Arcade.World#timeScale}.
  * @property {Phaser.Types.Math.Vector2Like} [gravity] - Sets {@link Phaser.Physics.Arcade.World#gravity}.
  * @property {number} [x=0] - Sets {@link Phaser.Physics.Arcade.World#bounds bounds.x}.