fixed marp config value in devcontainer

Author: codebytes

.devcontainer/slides/devcontainer.json

@@ -25,7 +25,7 @@
 	"customizations": {
 		"vscode": {
 			"settings": {
-				"markdown.marp.enableHtml" : true,
+				"markdown.marp.html": "all",
 				"markdown.marp.themes": [
 					"./slides/themes/custom.css",
 					"./slides/themes/custom-default.css",