update module docs and sphinx config

README.md

@@ -1,5 +1,6 @@
 # Overview
-Package summary goes here, ideally with a diagram
+Minimal framework for ML modeling, supporting advanced dataset operations and
+streamlined training workflows.
 
 # Install
 The `trainlib` package can be installed from PyPI:
@@ -85,7 +86,7 @@ pip install trainlib
   class SequenceDataset[I, **P](HomogenousDataset[int, I, I, P]):
       ...
   
-  class TupleDataset[I](SequenceDataset[tuple[I, ...], ??]):
+  class TupleDataset[I](SequenceDataset[tuple[I, ...], "?"]):
       ...
   ```