clarify the use of ENV variables

.env.example

@@ -1,23 +1,4 @@
-HF_API_TOKEN="<USE YOUR OWN>"
-MICROSERVICE_API_SECRET_TOKEN="<USE YOUR OWN>"
-
-# you can use this to bypass AiTube client URL
-#AITUBE_URL="https://aitube.at"
-#AITUBE_URL="http://localhost:3000"
-
-AI_TUBE_API_SECRET_JWT_KEY=""
-AI_TUBE_API_SECRET_JWT_ISSUER=""
-AI_TUBE_API_SECRET_JWT_AUDIENCE=""
-
-# ------------- HUGGING FACE OAUTH -------------
-NEXT_PUBLIC_ENABLE_HUGGING_FACE_OAUTH=""
-NEXT_PUBLIC_ENABLE_HUGGING_FACE_OAUTH_WALL=""
-NEXT_PUBLIC_HUGGING_FACE_OAUTH_CLIENT_ID=""
-
-# this one must be kept secret (and is unused for now)
-HUGGING_FACE_OAUTH_SECRET=""
-
-# ----------- RATE LIMIT -------
-ENABLE_RATE_LIMIT=""
-UPSTASH_REDIS_REST_URL=""
-UPSTASH_REDIS_REST_TOKEN=""
+# Currently Clapper doesn't require any environment variable
+#
+# This is something that might be used in the future to customize a deployment,
+# eg. to set the domain name, enable or disable some features etc..