Fixes setting form customizer list from to root site. Closes #460 (#469)

## 🎯 Aim

Fixes setting form customizer list from to root site

## 📷 Result


![image](https://github.com/user-attachments/assets/43589c65-b3f2-456a-918a-34d33fb243b7)


![image](https://github.com/user-attachments/assets/89a2531e-81ea-4b91-b804-dd4fefbe1f35)


## ✅ What was done

- [X] Updated URL validation

## 🔗 Related issue

Closes: #460

Author: Adam-it

src/services/actions/CliActions.ts

@@ -1027,12 +1027,8 @@ export class CliActions {
     const relativeUrl = await window.showInputBox({
       prompt: 'Enter the relative URL of the site',
       ignoreFocusOut: true,
-      placeHolder: 'e.g., sites/sales',
+      placeHolder: 'e.g., sites/sales or leave blank for root site',
       validateInput: (input) => {
-        if (!input) {
-          return 'site URL is required';
-        }
-
         const trimmedInput = input.trim();
 
         if (trimmedInput.startsWith('https://')) {