docs: update list of supported wheel platforms / architectures (#105)

Also, note deprecated status of 'manylinux1' wheels.

README.md

@@ -9,19 +9,30 @@ C toolchain.
 
 # Currently Published Wheels
 
-Wheels are currently published for Python 3.6, 3.7, 3.8, 3.9 for multiple
-architectures. For information on building your own, please view [BUILDING.md](BUILDING.md).
+Wheels are currently published for Python 3.6, 3.7, 3.8, 3.9, 3.10, and
+pypy-3.7 for multiple architectures. For information on building your own,
+please view [BUILDING.md](BUILDING.md).
+
 
 ## Linux
+
 Wheels are published for the following platforms / architectures:
 
-- `manylinux1` platform, `x86_64` architecture
-- `manylinux2010` platform, `x86_64` architecture
-- `manylinux2014` platform, `x86_64` architecture
+- `manylinux2010` platform, `x86_64` and `1686` architectures
 - `manylinux2014` platform, `aarch64` architecture
 
+### Deprecated
+
+- `manylinux1` platform, `x86_64` architecture wheels will be built until
+  2021-12-31, when the PyPA group drops support for the `manylinux1` image.
+  See: https://github.com/pypa/manylinux/issues/994 
+
+
 ## Mac OS
-Wheels are published for `x86_64` architectures
+
+Wheels are published for `x86_64` and `universal2` architectures.
+
 
 ## Windows
+
 Wheels are published for `win32` and `win_amd64` architectures.