Add possibility to change price axis text color

[kirchet]

Is your feature request related to a problem? Please describe.

For now we have ability to choose color for all scales:

lightweight-charts/src/model/layout-options.ts

Line 65 in f28f811

textColor: string;

Describe the solution you'd like

We can add an additional option like textColor in PriceScaleOptions. So the library should use this color to paint text on a scale if this color is provided via options.

lightweight-charts/src/model/price-scale.ts

Lines 89 to 170 in f28f811

	export interface PriceScaleOptions {
	/**
	* Autoscaling is a feature that automatically adjusts a price scale to fit the visible range of data.
	* Note that overlay price scales are always auto-scaled.
	*
	* @defaultValue `true`
	*/
	autoScale: boolean;
	/**
	* Price scale mode.
	*
	* @defaultValue {@link PriceScaleMode.Normal}
	*/
	mode: PriceScaleMode;
	/**
	* Invert the price scale, so that a upwards trend is shown as a downwards trend and vice versa.
	* Affects both the price scale and the data on the chart.
	*
	* @defaultValue `false`
	*/
	invertScale: boolean;
	/**
	* Align price scale labels to prevent them from overlapping.
	*
	* @defaultValue `true`
	*/
	alignLabels: boolean;
	/**
	* Price scale margins.
	*
	* @defaultValue `{ bottom: 0.1, top: 0.2 }`
	* @example
	* ```js
	* chart.priceScale('right').applyOptions({
	* scaleMargins: {
	* top: 0.8,
	* bottom: 0,
	* },
	* });
	* ```
	*/
	scaleMargins: PriceScaleMargins;
	/**
	* Set true to draw a border between the price scale and the chart area.
	*
	* @defaultValue `true`
	*/
	borderVisible: boolean;
	/**
	* Price scale border color.
	*
	* @defaultValue `'#2B2B43'`
	*/
	borderColor: string;
	/**
	* Show top and bottom corner labels only if entire text is visible.
	*
	* @defaultValue `false`
	*/
	entireTextOnly: boolean;
	/**
	* Indicates if this price scale visible. Ignored by overlay price scales.
	*
	* @defaultValue `true` for the right price scale and `false` for the left
	*/
	visible: boolean;
	/**
	* Draw small horizontal line on price axis labels.
	*
	* @defaultValue `false`
	*/
	ticksVisible: boolean;
	}

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