Applying matrix operations to `Fit`

`LinearAlgebra` defines operations such as `det()` on `Factorization` types such as `cholesky` etc.
currently to calculate this, we need a tree such as
```julia
det(get_decomposition(get_feature_factors(fit::Fit)))
```
It would be nice to reduce this to `det(fit::Fit)` and returning sensible options such as
- In the applicable factorizations, the usual determinant
- In the pseudo inverse case, the det of the original matrix,
- In the `svd` factorization perhaps the product of singular values (note, this gives only the `abs(det(fit))` - presumable why it is not in the list of applicable factorizations by `LinearAlgebra`)
etc.

PS: The determinant is so far the only operation I've needed but perhaps there might be other useful ones.