Remove unnecessary 'on' from en/libraries page
Merge pull request #772 from j1wilmot/patch-1

Remove unnecessary 'on' from libraries page (en)
Fix small typo in _config.yml (pt)
Add languages_heading (pt)
Add credits to _config.yml (pt)
Add unmaintained notice in portuguese (pt)

It's more useful to have an unmaintained notice in portuguese than english.
Add pt/about/website/index.md (pt)
Add /pt/about/logo/ (pt)