Display the diff between revisions

[leandrocp]

On the revisions tab, it should display a diff representation of what actually changed between revisions otherwise it's hard to spot the differences between revisions.

For text content we can use https://hex.pm/packages/text_diff and for relational data we might display a similar representation with added/removed/changed lines and diff the content of changes lines, for example a meta tag that changed the content only but kept the same name.