Add herb to the devcontainer

Author: rafaelfranca

.devcontainer/devcontainer.json

@@ -9,6 +9,9 @@
 
 	// Configure tool-specific properties.
 	"customizations": {
+		"vscode": {
+			"extensions": ["marcoroth.herb-lsp"]
+		}
 	},
 
 	// Use 'forwardPorts' to make a list of ports inside the container available locally.