Supported CPython releases

> Consolidates discussion in https://github.com/conda-forge/conda-forge-pinning-feedstock/issues/5013

The general rule @conda-forge/python team follows is:

**CPython `3.X` is supported until EOL or until Python `3.(X+5).rc1` is released (and packaged) whichever comes first.**

Since [PEP 602](https://peps.python.org/pep-0602) (2019), the Python release cadence is annual, with five years of support. This means that, since Python 3.8, October is the month where old versions go EOL and new versions are published. RCs are usually published around April/May.

Taking into account that the RC needs some time to be packaged in conda-forge, **users can expect the `python` pinning matrix to be updated somewhere in Summer every year**. This is of course a guideline with no guarantees and subject to the availability of volunteer efforts.

Check the [Status of Python versions docs](https://devguide.python.org/versions/) for more information about the Python release cycle.