Clarify config necessary for exposing container port

If Rocket is not configured to listen on 0.0.0.0:8000, exposing port
8000 on the inside to a chosen port (2399 by default), will not work.

README.md

@@ -43,7 +43,7 @@ port = 2399
 This will work independent of the type of build. For more about Rocket's
 configuration, see: <https://rocket.rs/v0.5-rc/guide/configuration/>.
 
-### Using cargo
+### Using Cargo
 
 Using Cargo it is easy to build and run Solar Grabber. just run:
 
@@ -57,7 +57,7 @@ $ cargo run --release
 
 ### Using Docker (Compose)
 
-Using `docker-compose` it is easy (to build and) run using a Docker image.
+Using Docker Compose it is easy (to build and) run using a Docker image.
 If you do not change `docker-compose.yml` it will use `Rocket.toml` from
 the current working directory as configuration:
 
@@ -66,7 +66,10 @@ $ docker-compose up
 ...
 ```
 
-To use Docker directly, run to build an image and the run it:
+Ensure that `Rocket.toml` listens on address `0.0.0.0` port `8000` for the
+exposing of the container port to the outside to work!
+
+Alternatively, to use Docker directly, run to build an image and the run it:
 
 ```console
 $ docker build --rm --tag solar-grabber:latest .

docker-compose.yml

@@ -6,9 +6,10 @@ services:
     build: .
     restart: unless-stopped
     ports:
+      # Ensure that Rocket listens on 0.0.0.0, port 8000 for this!
       - 2399:8000
-    # Use a `Rocket.toml` or configure the credentials using environment variables below
     volumes:
+      # Use a `Rocket.toml` or configure the credentials using environment variables below
       - ./Rocket.toml:/app/Rocket.toml
     environment:
       ROCKET_LOG_LEVEL: normal  # Available levels are: off, debug, normal, critical