feat(ui5-range-slider): focus and keyboard handling implementation (#2620)

Author: ndeshev

packages/main/src/RangeSlider.hbs

@@ -1,14 +1,14 @@
 {{>include "./SliderBase.hbs"}}
 
 {{#*inline "handles"}}
-	<div class="ui5-slider-handle ui5-slider-handle--start" style="{{styles.startHandle}}">
+	<div class="ui5-slider-handle ui5-slider-handle--start" style="{{styles.startHandle}}" tabindex="{{tabIndex}}" @focusout="{{_onfocusout}}" @focusin="{{_onfocusin}}">
 		{{#if showTooltip}}
 			<div class="ui5-slider-tooltip ui5-slider-tooltip--start" style="{{styles.tooltip}}">
 				<span class="ui5-slider-tooltip-value">{{tooltipStartValue}}</span>
 			</div>
 		{{/if}}
 	</div>
-	<div class="ui5-slider-handle ui5-slider-handle--end" style="{{styles.endHandle}}">
+	<div class="ui5-slider-handle ui5-slider-handle--end" style="{{styles.endHandle}}" tabindex="{{tabIndex}}" @focusout="{{_onfocusout}}" @focusin="{{_onfocusin}}">
 		{{#if showTooltip}}
 			<div class="ui5-slider-tooltip ui5-slider-tooltip--end" style="{{styles.tooltip}}">
 				<span class="ui5-slider-tooltip-value">{{tooltipEndValue}}</span>