Footnotes with code block fail with bootstrap v5

[banfai]

vignettes/test/rendering.Rmd L16-L18
If we change those to

Nay[^footnote]

[^footnote]: Including **footnotes** with embedded code:
```r
1 + 2
```
😢 

then it stops working with

Error in vapply(footnotes, FUN.VALUE = character(1), function(x) { : 
  values must be length 1,
 but FUN(X[[1]]) result is length 3

pkgdown/R/tweak-tags.R

Line 156 in ae7363f

as.character(xml2::xml_children(x), options = character())

returns a length-3 vector instead of length-1