Add supporters page

[choldgraf]

This updates our "supporters" pages so that they are a bit more discoverable and cleanly separated. Here are the major changes:

• Organizations that employ team members are now listed on the "our team" page, to differentiate from cloud/financial support
• We now have a dedicated page to list supporters of cloud/financial
• We store this information in YAML files, so it is easier to programmatically read and can be the source of truth
• The Binder federation page now focuses on the domains and logos, rather than "funded by etc" since we have the supporters page for those thanks now.
• I updates some of our conf.py scripts to be easier to read and maintain

[manics]

RTD failure:

Running Sphinx v4.5.0
repo2docker page does not exist, downloading from repo2docker docs. config_files.rst
repo2docker page does not exist, downloading from repo2docker docs. howto/languages.rst
repo2docker page does not exist, downloading from repo2docker docs. howto/user_interface.rst
repo2docker page exists, skipping download. Delete it to re-download. howto/lab_workspaces.rst 
Traceback (most recent call last):
  File "/home/docs/checkouts/readthedocs.org/user_builds/mybinder/checkouts/262/doc/_data/scripts/gen_federation_md.py", line 4, in <module>
    import pandas as pd
ModuleNotFoundError: No module named 'pandas'
Traceback (most recent call last):
  File "/home/docs/checkouts/readthedocs.org/user_builds/mybinder/checkouts/262/doc/_data/scripts/gen_support_md.py", line 4, in <module>
    import pandas as pd
ModuleNotFoundError: No module named 'pandas'

[choldgraf]

Ah good call - I've removed the pandas code from those scripts, and have also added a cross-link to the "our projects" page and links to the github repositories.

[choldgraf]

Thanks @manics for the review! I will merge this one in so that we can keep these docs up to date, and will iterate in subsequent PRs if there are more things to change!