Improve UX for markdown snippets (microsoft#146431)

Allow to directly paste a link markdown when using the `link` and `image` snippets

Author: nesk

extensions/markdown-basics/snippets/markdown.code-snippets

@@ -71,12 +71,12 @@
 	},
 	"Insert link": {
 		"prefix": "link",
-		"body": "[${TM_SELECTED_TEXT:${1:text}}](https://${2:link})$0",
+		"body": "[${TM_SELECTED_TEXT:${1:text}}](${2:https://})$0",
 		"description": "Insert link"
 	},
 	"Insert image": {
 		"prefix": "image",
-		"body": "![${TM_SELECTED_TEXT:${1:alt}}](https://${2:link})$0",
+		"body": "![${TM_SELECTED_TEXT:${1:alt}}](${2:https://})$0",
 		"description": "Insert image"
 	},
 	"Insert strikethrough": {