feat(Interaction): add artificial pusher controllable

The Artificial Pusher is a simulated pusher that uses no Unity
physics to move the pusher. It has fewer features than the
Physics Pusher but won't have the issues that the physics system
can cause.

Assets/VRTK/Documentation/API.md

@@ -14,6 +14,7 @@ This file describes all of the public methods, variables and events utilised by
    * [Secondary Controller Grab Actions](#secondary-controller-grab-actions-vrtksourcescriptsinteractionssecondarycontrollergrabactions)
    * [Controllables](#controllables-vrtksourcescriptsinteractionscontrollables)
      * [Physics Controllables](#physics-controllables-vrtksourcescriptsinteractionscontrollablesphysics)
+     * [Artificial Controllables](#artificial-controllables-vrtksourcescriptsinteractionscontrollablesartificial)
  * [Presence](#presence-vrtksourcescriptspresence)
  * [UI](#ui-vrtksourcescriptsui)
  * [3D Controls](#3d-controls-vrtksourcescriptscontrols3d)
@@ -6395,6 +6396,95 @@ The GetControlJoint method returns the joint associated with the control.
 
 ---
 
+# Artificial Controllables (VRTK/Source/Scripts/Interactions/Controllables/Artificial)
+
+A collection of scripts that provide artificial simulated controls that mimiic real life objects.
+
+ * [Artificial Pusher](#artificial-pusher-vrtk_artificialpusher)
+
+---
+
+## Artificial Pusher (VRTK_ArtificialPusher)
+ > extends [VRTK_BaseControllable](#base-controllable-vrtk_basecontrollable)
+
+### Overview
+
+An artificially simulated pushable pusher.
+
+**Required Components:**
+ * `Collider` - A Unity Collider to determine when an interaction has occured. Can be a compound collider set in child GameObjects. Will be automatically added at runtime.
+
+**Script Usage:**
+ * Place the `VRTK_ArtificialPusher` script onto the GameObject that is to become the pusher.
+
+### Inspector Parameters
+
+ * **Pressed Distance:** The distance along the `Operate Axis` until the pusher reaches the pressed position.
+ * **Min Max Limit Threshold:** The threshold in which the pusher's current normalized position along the `Operate Axis` has to be within the minimum and maximum limits of the pusher.
+ * **Resting Position:** The normalized position of the pusher between the original position and the pressed position that will be considered as the resting position for the pusher.
+ * **Resting Position Threshold:** The normalized value that the pusher can be from the `Resting Position` before the pusher is considered to be resting when not being interacted with.
+ * **Press Speed:** The speed in which the pusher moves towards to the `Pressed Distance` position.
+ * **Return Speed:** The speed in which the pusher will return to the `Target Position` of the pusher.
+
+### Class Methods
+
+#### GetValue/0
+
+  > `public override float GetValue()`
+
+ * Parameters
+   * _none_
+ * Returns
+   * `float` - The actual position of the pusher.
+
+The GetValue method returns the current position value of the pusher.
+
+#### GetNormalizedValue/0
+
+  > `public override float GetNormalizedValue()`
+
+ * Parameters
+   * _none_
+ * Returns
+   * `float` - The normalized position of the pusher.
+
+The GetNormalizedValue method returns the current position value of the pusher normalized between `0f` and `1f`.
+
+#### IsResting/0
+
+  > `public override bool IsResting()`
+
+ * Parameters
+   * _none_
+ * Returns
+   * `bool` - Returns `true` if the pusher is currently at the resting position.
+
+The IsResting method returns whether the pusher is currently at it's resting position.
+
+#### SetStayPressed/1
+
+  > `public virtual void SetStayPressed(bool state)`
+
+ * Parameters
+   * `bool state` - The state to set the `Stay Pressed` parameter to.
+ * Returns
+   * _none_
+
+The SetStayPressed method sets the `Stay Pressed` parameter to the given state and if the state is false and the pusher is currently pressed then it is reset to the original position.
+
+#### SetPositionTarget/1
+
+  > `public virtual void SetPositionTarget(float normalizedTarget)`
+
+ * Parameters
+   * `float normalizedTarget` - The `Position Target` to set the pusher to between `0f` and `1f`.
+ * Returns
+   * _none_
+
+The SetPositionTarget method sets the `Position Target` parameter to the given normalized value.
+
+---
+
 # Presence (VRTK/Source/Scripts/Presence)
 
 A collection of scripts that provide the ability to deal with tracking the world around the user in the scene.
@@ -8481,6 +8571,19 @@ The GetGPUTimeLastFrame retrieves the time spent by the GPU last frame, in secon
 
 The Vector2ShallowCompare method compares two given Vector2 objects based on the given fidelity, which is the equivalent of comparing rounded Vector2 elements to determine if the Vector2 elements are equal.
 
+#### Vector3ShallowCompare/3
+
+  > `public static bool Vector3ShallowCompare(Vector3 vectorA, Vector3 vectorB, float threshold)`
+
+ * Parameters
+   * `Vector3 vectorA` - The Vector3 to compare against.
+   * `Vector3 vectorB` - The Vector3 to compare with
+   * `float threshold` - The distance in which the two Vector3 objects can be within to be considered true
+ * Returns
+   * `bool` - Returns `true` if the given Vector3 objects are within the given threshold distance.
+
+The Vector3ShallowCompare method compares two given Vector3 objects based on the given threshold, which is the equavelent of checking the distance between two Vector3 objects are above the threshold distance.
+
 #### NumberPercent/2
 
   > `public static float NumberPercent(float value, float percent)`