added the missing .env.example file in supabase directory

Author: Amiralizim

supabase/.env.example

@@ -0,0 +1,7 @@
+STRIPE_SECRET_KEY="YOUR_STRIPE_SECRET_KEY"
+STRIPE_WEBHOOK_SIGNING_SECRET="YOUR_STRIPE_WEBHOOK_SIGNING_SECRET"
+POSTHOG_CLIENT_KEY="YOUR_POSTHOG_CLIENT_KEY"
+POSTMARK_SERVER_TOKEN="YOUR_POSTMARK_SERVER_TOKEN"
+POSTMARK_FROM_EMAIL="YOUR_POSTMARK_FROM_EMAIL"
+SUPABASE_URL="YOUR_SUPABASE_URL"
+SUPABASE_SERVICE_ROLE_KEY="YOUR_SUPABASE_SERVICE_ROLE_KEY"