Store History Diff Changes in backend

When looking at the history of a file, we want to be able to see the incremental changes (compared to its previous version).

An example can be seen below (source: VTK Wiki)

Or a current view of our frontend:

In the screenshot shown above, the diff is currently calculated by the frontend. However, this is not ideal for a couple of reasons. One of them being that we cannot efficiently show high-level previews of the changes of each revision (as depicted on the image above with +22 - 18). Furthermore, the front-end solutions are rather limited, and I think ideally we want a two-column comparison (however, this can still be discussed. As a result, the diffs should be stored in the backend.