sparkchart.go
func (b *SparkChart) SetValueWidth(width int) {
	b.mtx.Lock()
	defer b.mtx.Unlock()

	b.valueWidth = width
}
func (b *SparkChart) SetValueWidth(width int) {
	b.mtx.Lock()
	defer b.mtx.Unlock()

	b.valueWidth = width
}
// SetValueWidth changes width of the value panel on the left