add MULTI_TAG_pnp to docs (#284)

* adding multi_tag_pnp to the docs

* changing five to six

* removing pnp

Author: jheidegger

source/docs/programming/photonlib/robot-pose-estimator.rst

@@ -31,7 +31,7 @@ The API documentation can be found in here: `Java <https://github.wpilib.org/all
 
 Creating a ``PhotonPoseEstimator``
 ----------------------------------
-The PhotonPoseEstimator has a constructor that takes an ``AprilTagFieldLayout`` (see above), ``PoseStrategy``, ``PhotonCamera``, and ``Transform3d``. ``PoseStrategy`` has five possible values:
+The PhotonPoseEstimator has a constructor that takes an ``AprilTagFieldLayout`` (see above), ``PoseStrategy``, ``PhotonCamera``, and ``Transform3d``. ``PoseStrategy`` has six possible values:
 
 * LOWEST_AMBIGUITY
     * Choose the Pose with the lowest ambiguity.
@@ -43,6 +43,8 @@ The PhotonPoseEstimator has a constructor that takes an ``AprilTagFieldLayout``
     * Choose the Pose which is closest to the last pose calculated.
 * AVERAGE_BEST_TARGETS
     * Choose the Pose which is the average of all the poses from each tag.
+* MULTI_TAG_PNP
+    * Calculates a new robot position estimate by combining all visible tags.
 
 .. tab-set-code::
    .. code-block:: java