[Timeline] New needs

[vvalentin-lucca]

Some feedback using the timeline component:

• [ ] .mod-dashed is not described in the doc;
• [x] .mods-number and .mod-checkedPastStep are not currently compatible;
• [ ] there's a need to pass larger titles to .timeline-step-title, which currently causes a vertical offset between the title and its bullet point;
• [ ] .timeline-step-title-icon doesn't have a top linked to its positioning, which can also sometimes shift it;
• [ ] what if you want to use .timeline-step-title-icon but don't want a title in the steps?
• [ ] in the examples, the latter is indicated as vertical, but is not in practice ;
• [ ] padding on left is not consistent.