Fix Category from dashboard to Dashboard to match the rest of the templates.

template/apps/heimdall.json

@@ -2,7 +2,7 @@
 	"categories": [
 		"Tools",
 		"Web",
-		"dashboard"
+		"Dashboard"
 	],
 	"description": "Heimdall is a way to organise all those links to your most used web sites and web applications in a simple way.",
 	"env": [