chore: clarify python version policy (#365)

* chore: clarify python version policy

* Update README.md

Co-authored-by: Jack Wotherspoon <jackwoth@google.com>

Co-authored-by: Jack Wotherspoon <jackwoth@google.com>

Author: kurtisvg

README.md

@@ -25,9 +25,6 @@ Currently supported drivers are:
  - [`pg8000`](https://github.com/tlocke/pg8000) (PostgreSQL)
  - [`pytds`](https://github.com/denisenkom/pytds) (SQL Server)
 
-## Supported Python Versions
-
-Currently Python versions >= 3.7 are supported.
 
 ## Installation
 
@@ -292,6 +289,14 @@ supported for 1 year.
 **Unsupported** - Any major version that has been deprecated for >=1 year is
 considered publicly unsupported.
 
+## Supported Python Versions
+
+We test and support at a minimum, every [active version until it's
+end-of-life date][pyver]. Changes in supported Python versions will be
+considered a minor change, and will be listed in the release notes. 
+
+[pyver]: https://devguide.python.org/#status-of-python-branches
+
 ### Release cadence
 This project aims for a minimum monthly release cadence. If no new
 features or fixes have been added, a new PATCH version with the latest