feat(render): support render snippets of chart

[Koooooo-7]

Description

Please share your ideas and awesome changes to let us know more :)

As per to the contribution and discussion in #410 .
Do the refine:

• Only support the RenderSnippets in chart.
• Refactor templates.
• Add BaseRender to make the interface implementation easier.
• Support extract options individually.
• Support multi render calls and update the before function re-trigger issues.

Example:

// create a new bar instance
	bar := charts.NewBar()
	// set some global options like Title/Legend/ToolTip or anything else
	bar.SetGlobalOptions(charts.WithTitleOpts(opts.Title{
		Title:    "My first bar chart generated by go-echarts",
		Subtitle: "It's extremely easy to use, right?",
	}))

	// Put data into instance
	bar.SetXAxis([]string{"Mon", "Tue", "Wed", "Thu", "Fri", "Sat", "Sun"}).
		AddSeries("Category A", generateBarItems()).
		AddSeries("Category B", generateBarItems())

	chartSnippet := bar.RenderSnippet()

	tmpl := "{{.Element  }} {{.Script}} {{.Option}}"
	t := template.New("snippet")
	t, err := t.Parse(tmpl)
	if err != nil {
		panic(err)
	}

	data := struct {
		Element template.HTML
		Script  template.HTML
		Option  template.HTML
	}{
		Element: template.HTML(chartSnippet.Element),
		Script:  template.HTML(chartSnippet.Script),
		Option:  template.HTML(chartSnippet.Option),
	}

	err = t.Execute(os.Stdout, data)
	if err != nil {
		panic(err)
	}

close #406

Type of change

• Bug fix (Non-breaking change which fixes an issue)
• New feature (Non-breaking change which adds functionality)
• Breaking change (Would cause existing functionality to not work as expected)
• Docs
• Others

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