Now that we support svg rendering we should consider adding support for rendered svg diff.

This shows the basic functionality in GitHub.

See live GitHub example (note: GitHub actually seems to have a bug in swipe mode when the SVG size has changed it shows both on tope of one-another)

Personally, I find the the onion skin mode to be the least helpful, but the other two modes are quite useful.

Request:

• Like GitHub, we should render the svg diff in PRs and commit diff view
• Like GitHub, we should have a toggle button to switch between code and render mode
• Unlike GitHub, the toggle button should be "sticky" between sessions/page-views, so that a user navigating between PR tabs doesn't have to repeatedly toggle the button.
• Unlike GitHub, the default toggle state should be configurable by either repository, user, or gitea instance