Add a spellchecking mode for sphinx and fix some typos

* The worst one was Persistant -> Persistent. This involved renaming
  PersistentConfig but the impact of that is considered minimal enough to be
  worth fixing.

docs/python_api/renderdoc/analysis.rst

@@ -84,8 +84,8 @@ Pixel History
 .. autoclass:: PixelValue
   :members:
 
-Shader Debuging
----------------
+Shader Debugging
+----------------
 
 .. autoclass:: DebugPixelInputs
   :members:

docs/python_api/renderdoc/pipelines/common.rst

@@ -164,6 +164,3 @@ Shader Messages
 
 .. autoclass:: renderdoc.ShaderComputeMessageLocation
   :members:
-
-
-* qrenderdoc.ShaderMessageViewer