chore: create .env.example for bootstrap nextjs (#22309)

examples/slack-clone/nextjs-slack-clone/.env.example

@@ -1,4 +1,4 @@
 # Get these from your API settings: https://supabase.com/dashboard/project/_/settings/api
 
 NEXT_PUBLIC_SUPABASE_URL=https://your-project.supabase.co
-NEXT_PUBLIC_SUPABASE_ANON_KEY=your-anon-key
+NEXT_PUBLIC_SUPABASE_ANON_KEY=your-anon-key

examples/slack-clone/nextjs-slack-clone/README.md

@@ -61,10 +61,10 @@ Simply clone this repo locally and proceed to the next section.
 
 ### Required configuration
 
-Copy the `.env.local.example` file into a file named `.env.local` in the root directory of the example:
+Copy the `.env.example` file into a file named `.env.local` in the root directory of the example:
 
 ```bash
-cp .env.local.example .env.local
+cp .env.example .env.local
 ```
 
 Set your Supabase details from [step 3](#3-get-the-url-and-key) above:

examples/user-management/nextjs-user-management/.env.example

@@ -0,0 +1,4 @@
+# Get these from your API settings: https://supabase.com/dashboard/project/_/settings/api
+
+NEXT_PUBLIC_SUPABASE_URL=https://your-project.supabase.co
+NEXT_PUBLIC_SUPABASE_ANON_KEY=your-anon-key