Add support for shared axes in subplots

[AngelEzquerra]

As discussed in the nim forum (https://forum.nim-lang.org/t/8569), I'm creating this issue to request support for Shared X-Axes. This is described in the plotly docs:

https://plotly.com/python/subplots/#subplots-with-shared-xaxes

I hope this can be added to nim-plotly as well, since I often find that it is very convenient to create a bunch of subplots that shared the same time axis.