Italics in generated indexes

[Siggy15]

It would be useful to be able to specifify a bit of formatting for index entries. For example, scientific names are typically written in italics: Homo sapiens

This could be simple and backwards compatible like this:

sigil_index_marker
sigil_index_marker-i

likewise:

sigil_index_marker-b
sigil_index_marker-u

in fact, if you parse the flags after the dash, many things would be possible:

sigil_index_marker-ibu

but plain italics is the thing that is most needed

[KevinH]

Simply add something unique to each entry itself and the use Sigil search and replace to add the proper css class.