[echarts] Initialize echarts with built in dark/light theme matching LogSeq system settings

[swarminglogic]

To my knowledge, echarts doesn't have a way to set/chose a predefined theme, except at init, with something like

var chart = echarts.init(dom, 'dark');

This makes renders difficult to read, without overriding individual colors (which is both verbose and tedious). The example here #19

Might instead look like:

I imagine the change would be something akin to #18

But in

logseq-fenced-code-plus/src/echarts.tsx

Line 47 in 8163254

const myChart = echarts.init(elRef.current)

Lastly,
Thanks for a great plugin.