DOC: Add Matti Picus to steering council page
DOC: Add Matti Picus to steering council page

Per announcement in https://mail.python.org/pipermail/numpy-discussion/2020-June/080760.html.

I've alphabetized the steering council names (some but not all had been
alphabetized). Added diacritical mark in Stéfan.

This page partially overlaps https://numpy.org/about/. Submitting a
separate PR.

I imagine at some point we want to transfer over the remaining contents
of this older page and cleanly remove it.

jakirkham/numpy,simongibbons/numpy,mhvk/numpy,anntzer/numpy,grlee77/numpy,pdebuyl/numpy,mhvk/numpy,madphysicist/numpy,pbrod/numpy,seberg/numpy,rgommers/numpy,grlee77/numpy,endolith/numpy,charris/numpy,endolith/numpy,mattip/numpy,madphysicist/numpy,madphysicist/numpy,rgommers/numpy,grlee77/numpy,mhvk/numpy,jakirkham/numpy,charris/numpy,numpy/numpy,pbrod/numpy,anntzer/numpy,pbrod/numpy,mhvk/numpy,rgommers/numpy,grlee77/numpy,pdebuyl/numpy,charris/numpy,numpy/numpy,pdebuyl/numpy,simongibbons/numpy,endolith/numpy,anntzer/numpy,simongibbons/numpy,jakirkham/numpy,numpy/numpy,simongibbons/numpy,charris/numpy,jakirkham/numpy,pbrod/numpy,numpy/numpy,mattip/numpy,seberg/numpy,simongibbons/numpy,jakirkham/numpy,mattip/numpy,seberg/numpy,mhvk/numpy,madphysicist/numpy,madphysicist/numpy,seberg/numpy,mattip/numpy,endolith/numpy,pdebuyl/numpy,anntzer/numpy,grlee77/numpy,rgommers/numpy,pbrod/numpy