Improved Customization process

Allow users to updated Theme Name, PHP Namespace, and Theme Description, without breaking the theme.
Avoid overwriting the .env file if it already exists in the WordPress root folder.

Allow user to change the namespace

The user is prompted with a question to update the namespace from Awps\ to whatever they like.
Also, the theme name will be renamed from Alecaddd WordPress Starter theme to the theme name specified on the command argument.

Thanks to @BaronVonPerko for the PR!