PYTHON-4054 Add ability to serve live docs (#1447)

Author: blink1073

CONTRIBUTING.md

@@ -172,14 +172,25 @@ request](https://help.github.com/articles/using-pull-requests). You
 might also use the GitHub
 [Edit](https://github.com/blog/844-forking-with-the-edit-button) button.
 
-We use the [Sphinx docstring format](https://sphinx-rtd-tutorial.readthedocs.io/en/latest/docstrings.html).
+We use [reStructuredText](https://www.sphinx-doc.org/en/master/usage/restructuredtext/basics.html) for all
+documentation including narrative docs, and the [Sphinx docstring format](https://sphinx-rtd-tutorial.readthedocs.io/en/latest/docstrings.html).
 
 You can build the documentation locally by running:
 
 ```bash
 tox -e doc
 ```
 
+When updating docs, it can be helpful to run the live docs server as:
+
+```bash
+tox -e doc-serve
+```
+
+Browse to the link provided, and then as you make changes to docstrings or narrative docs,
+the pages will re-render and the browser will automatically refresh.
+
+
 ## Running Tests Locally
 
 -   Ensure you have started the appropriate Mongo Server(s).

tox.ini

@@ -21,6 +21,8 @@ envlist =
     typecheck,
     # Build sphinx docs
     doc,
+    # Server live sphinx docs
+    doc-serve,
     # Test sphinx docs
     doc-test,
     # Linkcheck sphinx docs
@@ -38,6 +40,7 @@ labels = # Use labels and -m instead of -e so that tox -m <label> fails instantl
     typecheck-pyright-strict = typecheck-pyright-strict
     typecheck = typecheck
     doc = doc
+    doc-serve = doc-serve
     doc-test = doc-test
     linkcheck = linkcheck
     test-mockupdb = test-mockupdb
@@ -134,7 +137,15 @@ description = build sphinx docs
 deps =
     -rdoc/docs-requirements.txt
 commands =
-    sphinx-build -E -W -b html doc ./doc/_build/html
+    sphinx-build -W -b html doc ./doc/_build/html
+
+[testenv:doc-serve]
+description = serve sphinx docs
+deps =
+    {[testenv:doc]deps}
+    sphinx-autobuild
+commands =
+    sphinx-autobuild -W -b html doc --watch ./pymongo --watch ./bson --watch ./gridfs ./doc/_build/serve
 
 [testenv:doc-test]
 description = run sphinx doc tests