Do not use emojis instead of words

[dbuenzli]

I just tested the beta because of an annoying preamble bug I had in 2.4. It's fixed :–)

But I just saw that in the breadcrumbs, the emoji 🏠 is used to denote top or index. These bring the following two problems:

1. Using emojis instead of words is bad for accessibility.
2. From a styling perspective, adding emojis or icons is best done through CSS like @yawaramin did in https://github.com/ocaml/odoc/pull/1089/files, this allows to have icons that are consistent with the style (e.g. that house emoji with odig's default stylesheet really screams on the page and needlessly attracts the eye).

[panglesd]

Yes, that is true. I would slightly be in favor of letting the driver choose a name (and make it "Index" in odoc_driver).