Clarify which part may not work for mypy users yet

Author: mikeshardmind

readme.md

@@ -93,7 +93,7 @@ The project currently uses pyright for development, and both pyright and mypy
 when ensuring the public api surface is well-typed and compatible with strict
 use of typechecking. The configurations used are in pyproject.toml.
 
-Mypy use is known to be broken currently, as mypy
+Mypy is known to be broken currently, for the cache decorators
 [discards type information in Callable aliases](https://github.com/python/mypy/issues/18842)
 
 Use of Any in a few places is *intentional* for internals.