The change in d801a6693c to search for
suffixes in `file-types` is too permissive: files like the tutor or
`*.txt` files are now mistakenly interpreted as R or perl,
respectively.
This change changes the syntax for specifying a file-types entry that
matches by suffix:
```toml
file-types = [{ suffix = ".git/config" }]
```
And changes the file-type detection to first search for any non-suffix
patterns and then search for suffixes only with the file-types entries
marked explicitly as suffixes.
17daf6ac0a