Add Pillow logo to README and PyPI

[hugovk]

Let's show the logo in the README and on PyPI!

Changes proposed in this pull request:

• Like Add a smaller logo to the README pillow-logo#3
• Convert README.rst to Markdown, because we cannot centre images with RST or place it after the page header ("Pillow")
  • Re: https://dustingram.com/articles/2018/03/16/markdown-descriptions-on-pypi/
• The badges table is in HTML, because native MD table require a top header

GitHub preview

https://github.com/hugovk/Pillow/tree/add-logo-to-readme

TestPyPI preview

https://test.pypi.org/project/Pillow/8.0.0.dev0/

[nulano]

• Convert README.rst to Markdown, because we cannot centre images with RST or place it after the page header ("Pillow")

  • Re: https://dustingram.com/articles/2018/03/16/markdown-descriptions-on-pypi/

I've been able to use :align: center in RST before. Is this directive producing undesired output, or is there a problem with PyPI's or GitHub's RST support?

[hugovk]

GitHub doesn't support :align: in RST.

• Image alignment not respected in reStructuredText github/markup#163

Demo: hugovk@05325e4

.. image:: https://raw.githubusercontent.com/python-pillow/pillow-logo/master/pillow-logo-248x250.png
    :width: 248px
    :height: 250px
    :align: center