Merge pull request #11367 from meeseeksmachine/auto-backport-of-pr-11365-on-3.2.x

Backport PR #11365 on branch 3.2.x (Adds command to docs to install canvas dependencies)

docs/source/developer/contributing.rst

@@ -171,6 +171,12 @@ Notes:
    installation, make sure Python 3.0+ is installed. Also, try using the
    Python 3.0+ version of ``pip`` or ``pip3 install -e .`` command to
    install JupyterLab from the forked repository.
+-  If you see an error that says ``Call to 'pkg-config pixman-1 --libs'
+   returned exit status 127 while in binding.gyp`` while running the 
+   ``pip install`` command above, you may be missing packages required
+   by ``canvas``. On macOS with Homebrew, you can add these packages by
+   running 
+   ``brew install pkg-config cairo pango libpng jpeg giflib librsvg``.
 -  The ``jlpm`` command is a JupyterLab-provided, locked version of the
    `yarn <https://yarnpkg.com/en>`__ package manager. If you have
    ``yarn`` installed already, you can use the ``yarn`` command when