Implement feature: settings - custom d3 path; maybe download from settings menu

[Dmytro-Shulha]

Since some plotly charts rely on D3 library, which is big and I do not want it to be part of plugin bundle, managing it's usage should be simplified.

As of now, the only way to use D3 is to download .min.js file from official site, place it somewhere in a vault and provide correct path in your dataviewjs block with chart code (using hardcoded output of 'create new chart' command).

Better way would be an option to set path to D3 in settings menu.
Downloading D3 lib also can be done from settings menu, but that might expose user to security risks and needs to be investigated.

This change will eliminate need to explicitly set path to D3 lib in each chart.

Separated from #4