Re-export all names from typing (python#196)

* Re-export all names from typing

Fixes python#50.

I decided to exclude top-level names that have a definite removal
timeline (io, re, ByteString); there's no point in re-exporting them
now.

Many other names are deprecated without a definite removal plan
(PEP 585). If they do get removed eventually, typing-extensions can
simply re-export the builtin/collections.abc names.

In the documentation, I add a separate section listing all the names
that are pure aliases for typing. This makes it easier to distinguish
the cases where there is something more interesting going on in
typing-extensions.

Co-authored-by: Alex Waygood <[email protected]>
Co-authored-by: Shantanu <[email protected]>

Author: 3 people

CHANGELOG.md

@@ -1,5 +1,8 @@
 # Unreleased
 
+- `typing_extensions` now re-exports all names in the standard library's
+  `typing` module, except the deprecated `ByteString`. Patch by Jelle
+  Zijlstra.
 - Due to changes in the implementation of `typing_extensions.Protocol`,
   `typing.runtime_checkable` can now be used on `typing_extensions.Protocol`
   (previously, users had to use `typing_extensions.runtime_checkable` if they