add cpp api reference (#618)

Summary: Pull Request resolved: #618

Differential Revision: D49924199

Author: JacobSzwejbka

.ci/docker/requirements-ci.txt

@@ -15,8 +15,11 @@ hypothesis==6.84.2
 parameterized==0.9.0
 
 # Doc build requirements
-sphinx==5.0.0
+sphinx==4.5.0
 sphinx-gallery
+breathe==4.35.0
+exhale==0.3.6
+docutils==0.16
 matplotlib
 # PyTorch Theme
 -e git+https://github.com/pytorch/pytorch_sphinx_theme.git#egg=pytorch_sphinx_theme