Sphinx panel

Fixes pytorch#73835.

The full context for this is detailed in the issue, but briefly:

- Adds `sphinx-panel`

Other PRs will demonstrate usage.
Pull Request resolved: pytorch#73836
Approved by: https://github.com/albanD

CONTRIBUTING.md

@@ -512,7 +512,7 @@ missing file warnings but will still complete. For example, to work on `jit.rst`
 
 ```bash
 cd docs/source
-ls | grep rst | grep -v index | grep -v jit | xargs rm
+find . -type f | grep rst | grep -v index | grep -v jit | xargs rm
 
 # Make your changes, build the docs, etc.
 

docs/requirements.txt

@@ -7,3 +7,4 @@ tensorboard
 # required to build torch.distributed.elastic.rendezvous.etcd* docs
 python-etcd>=0.4.5
 sphinx_copybutton
+sphinx-panels

docs/source/conf.py

@@ -57,12 +57,16 @@
     'sphinxcontrib.katex',
     'sphinx.ext.autosectionlabel',
     'sphinx_copybutton',
+    'sphinx_panels'
 ]
 
 # build the templated autosummary files
 autosummary_generate = True
 numpydoc_show_class_members = False
 
+# Theme has bootstrap already
+panels_add_bootstrap_css = False
+
 # autosectionlabel throws warnings if section names are duplicated.
 # The following tells autosectionlabel to not throw a warning for
 # duplicated section names that are in different documents.