Document how to install PhotonLib of specific version (#1392)

docs/source/docs/installation/updating.rst

@@ -33,7 +33,7 @@ Installing Pre-Release Versions
 
 Pre-release/development version of PhotonVision can be tested by installing/downloading artifacts from Github Actions (see below), which are built automatically on commits to open pull requests and to PhotonVision's ``master`` branch, or by :ref:`compiling PhotonVision locally <docs/contributing/building-photon:Build Instructions>`.
 
-.. warning:: If testing a pre-release version of PhotonVision with a robot, PhotonLib must be updated to match the version downloaded! If not, packet schema definitions may not match and unexpected things will occur.
+.. warning:: If testing a pre-release version of PhotonVision with a robot, PhotonLib must be updated to match the version downloaded! If not, packet schema definitions may not match and unexpected things will occur. To update PhotonLib, refer to :ref:`installing specific version of PhotonLib<docs/programming/photonlib/adding-vendordep:Install Specific Version - Java/C++>`.
 
 Github Actions builds pre-release version of PhotonVision automatically on PRs and on each commit merged to master. To test a particular commit to master, navigate to the `PhotonVision commit list <https://github.com/PhotonVision/photonvision/commits/master/>`_ and click on the check mark (below). Scroll to "Build / Build fat JAR - PLATFORM", click details, and then summary. From here, JAR and image files can be downloaded to be flashed or uploaded using "Offline Update".
 

docs/source/docs/programming/photonlib/adding-vendordep.rst

@@ -38,3 +38,9 @@ Add photonlibpy to `pyproject.toml`.
     ]
 
 See `The WPILib/RobotPy docs <https://docs.wpilib.org/en/stable/docs/software/python/pyproject_toml.html>`_ for more information on using `pyproject.toml.`
+
+Install Specific Version - Java/C++
+-----------------------------------
+In cases where you want to test a specific version of PhotonLib, make sure you have finished the steps in Online Install - Java/C++ and then manually change the version string in the photonlib vendordep json file(at ``/path/to/your/project/vendordep/photonlib.json``) to your desired version.
+
+.. image:: images/photonlib-vendordep-json.png