This uses a new feature from snapbox that let's us render terminal
styling in SVG files. This let's us see / visualize ANSI escape codes,
including in github's UI (will render images, including side-by-side
images for diffs).
Currently, the UI tests are
- `cargo add`
- `cargo new`
- `cargo remove`
- `init`
One of these is not like the others. This change renames `init` to
`cargo_init` to suggest it is the UI tests for the `cargo init` command,
rather than `init` functionality.