Improve Tutorials landing page to auto-detect more data

[mDuo13]

As noted in #3509 , the tutorials landing page has some very long data objects defining what contents get listed on the page. Since keeping these in sync with the files themselves is likely to become a maintenance burden, we would like to auto-detect more data to lessen the maintenance burden. The page already uses a plugin that auto-detects which programming languages each file contains, so that's a good start.