Generate a page with baseline comparison for pypy.org

[StanFromIreland]

The chart on https://pypy.org/ is currently out of date. If we embed it, it won't go stale. And, it also makes it interactive.

With this, we'll be able to replace the image in index.rst with something like:

.. raw:: html

   <iframe src="https://speed.pypy.org/embed/comparison/"
           title="PyPy vs CPython benchmark comparison"
           style="border: 0; width: 100%; height: 480px"
           loading="lazy"></iframe>

[mattip]

Nice. Two comments:

• I am a little worried the two implementations could get out of sync. Can we make them share the graph generating code?
• Currently pypy.org has the text

On average, PyPy is about 3 times faster than CPython 3.11. We currently support python 3.11 and 2.7.

It would be nice to get the "3 times faster" also from speed.pypy.org, or rework the text from speed.pypy.org and share the same text: "The geometric average of all benchmarks is 0.22 or 4.5 times faster than cpython"

[mattip]

Sorry for the feature creep, it is fine to declare that out of scope.