Support infinity for generators column_span parameter

[jeparlefrancais]

Closes #350

A small fix to deserialize the column_span parameter on the dense and readable generator as a float number. That way, since the config is read as json5, the max column can be set to infinity:

{
    generator: { name: "dense", column_span: Infinity },
}

• add entry to the changelog

[github-actions]

Coverage after merging read-column-span-as-float into main will be

85.05%

Coverage Report for Changed Files

File	Stmts	Branches	Funcs	Lines	Uncovered Lines
src/frontend
configuration.rs	82.02%	100%	80.60%	82.28%	114–117, 121–125, 129–132, 136–140, 143–146, 149–154, 157–159, 241–260, 262–263, 345–349, 81–83, 94–97
src/utils
mod.rs	96.48%	100%	96%	96.58%	65–66, 73
serde_usize_from_float.rs	57.89%	100%	100%	55.56%	12, 17–19, 22, 25–27