Why takeExtensions returns dot?

Hi,

I suggest to add an alternative to takeExtensions which drops heading dot

```haskell
takeExtensions' "/directory/path.ext" == Just "ext"
takeExtensions' "file.tar.gz" == Just "tar.gz"
```

Start by locating the takeExtensions entry point and the surrounding tests or documentation in the filepath library. Check the existing dot-preserving behavior, then define the alternative's behavior for the examples in the issue and verify both examples and existing behavior with the test suite.

Written by the indexing model from the issue text.