[UWP Renderer] RTL is not working within ShowCard

Platform

• UWP

Issue

RTL is not working within ShowCard.

Example card

{
	"$schema": "http://adaptivecards.io/schemas/adaptive-card.json",
	"type": "AdaptiveCard",
	"version": "1.5",
	"body": [
		{
			"type": "TextBlock",
			"text": "Please select your language:",
			"wrap": true
		}
	],
	"actions": [
		{
			"type": "Action.ShowCard",
			"title": "عربي",
			"card": {
				"type": "AdaptiveCard",
				"rtl": true,
				"body": [
					{
						"type": "TextBlock",
						"text": "إستمارة تسجيل"
					}
				]
			}
		}
	]
}

Use the supplied Adaptive Card JSON as the reproduction case and begin at the UWP renderer's Action.ShowCard handling. Verify how the nested card's rtl=true value is applied; done means the Arabic ShowCard content renders right-to-left in UWP without regressing the outer card.