Automatically Catch Sphinx Errors (#8530)

* clean up some Sphinx warnings

* first attempt at a doc-test pipeline job

* fix formatting

* fix test name

* set env for bash

* try bash vs script

* maybe it didn't like me setting 'PATH'...derp

* drop use of venv

* sphinx-build isn't a py script

* try activating venv

* docs: remove unused html_static tags

* clean up final sphinx build errors for certbot

* clean up final sphinx build errors for acme

* better names for docs pipeline

* fix spelling

* add docs_extras to setup.py

* remove temp doc-testing pipeline; add template to main.yml

* rearrange pipeline execution; run sphinx builds in one job

* add documentation note to compat.os

* add uninstall.rst as a sub-toctree to avoid build error

certbot/docs/api/certbot.compat.os.rst

@@ -2,6 +2,4 @@ certbot.compat.os module
 ========================
 
 .. automodule:: certbot.compat.os
-    :members:
-    :undoc-members:
-    :show-inheritance:
+    :members: chmod, umask, chown, open, mkdir, makedirs, rename, replace, access, stat, fstat