allow boxes of different height on the timeline graph

[mvonweis]

Hi,

I have a situation where I would like to visualize the burn rate of projects on a timeline. It would be most logical to present this as the height of each box. Currently every row in the timeline graph is of uniform height, and there is no provision for changing the size.

Would it be possible to add a new feature for varying heights within the timeline graph? Something like this (in Plotly Express):
`df = pd.DataFrame([
dict(Task="Project A", Start='2009-01-01', Finish='2009-02-28', Burnrate=200),
dict(Task="Project B", Start='2009-03-05', Finish='2009-04-15', Burnrate=75),
dict(Task="Project C", Start='2009-02-20', Finish='2009-05-30', Burnrate=110)
])

fig = px.timeline(df, x_start="Start", x_end="Finish", y="Task", size="Burnrate")
fig.show()`

Also, while the boxes can be drawn very slim (low size values), there probably needs to be a minimum row height determined by the label text.

Something similar could probably be built by stacking bar charts or area plots in one facet column, but I think the resulting graph would be too high and might also be visually too complicated.

Cheers,
--Martin