Feature: Channels lines width proportional with channel capacity

[parti-zanu]

Channel line width should be proportional with channel capacity.

It could factor in some scale mapping, eg if x sat is the largest channel (100%),

• a channel between 75%-100% can be 8px wide
• 50%-100% 4px wide
• 1%-50% 1px wide

[chemicstry]

It was implemented in the old Vis.js view using logarithmic scale but the difference between widths was very tiny. Probably because channels are of very similar capacity right now (in terms of log scale). I will try to implement this on the new view and tune the formula a bit.