[transformation] alt text with both single and double quotes has double-escaped double quotes

``` r
tmp <- withr::local_tempfile()
writeLines(c(""), tmp)
pegboard::Episode$new(tmp)$use_sandpaper()$show()
#> ---
#> ~
#> ---
#>
#> {alt="\\"data\\" is a 3 by 3 numpy 'array'"}
```

^{Created on 2023-03-28 with [reprex v2.0.2](https://reprex.tidyverse.org)}

Start with the reproducible R example using pegboard::Episode$new(tmp)$use_sandpaper()$show(), then trace the transformation of the image alt text containing both quote types. Done means the transformed output preserves the intended single and double quotes without double-escaping the double quotes.

Written by the indexing model from the issue text.