[#1390] Update instructions to include graphviz

Author: ReeceHumphreys

docs/source/Build/installOnMacOS.rst

@@ -42,6 +42,11 @@ In order to run Basilisk on macOS, the following software is necessary:
 #. (Optional) Get the `PyCharm <https://www.jetbrains.com/pycharm/>`__
    application to be able to edit python source files
 
+#. (Optional, required to build docs locally) Install `Doxygen <https://www.doxygen.nl>`__ and
+   `Graphviz <https://graphviz.org>`__ via Homebrew::
+
+     $ brew install doxygen graphviz
+
 Install Python 3
 ----------------
 To install Python 3 on macOS there are two common options:

docs/source/conf.py

@@ -9,6 +9,7 @@
 # -- Path setup --------------------------------------------------------------
 
 import datetime
+import shutil
 # If extensions (or modules to document with autodoc) are in another directory,
 # add these directories to sys.path here. If the directory is relative to the
 # documentation root, use os.path.abspath to make it absolute, like shown here.
@@ -133,6 +134,8 @@ def build_supportdata_index_rst(output_file: str):
 ]
 
 graphviz_output_format = "svg"
+_dot_candidates = ["/opt/homebrew/bin/dot", "/usr/local/bin/dot"]
+graphviz_dot = shutil.which("dot") or next((p for p in _dot_candidates if os.path.exists(p)), "dot")
 
 # Use MathJax SVG output instead of CHTML to avoid browser/font-metric
 # rendering artifacts (e.g., vertically offset multi-character symbols).
@@ -323,7 +326,6 @@ def build_supportdata_index_rst(output_file: str):
 # breathe_projects = {"Basilisk": "../../src/*"}
 
 from glob import glob
-import shutil
 
 class fileCrawler():
     def __init__(self, newFiles=False):