Add clarifying information for CurseForge API keys (#3594)

docs/types-and-platforms/mod-platforms/auto-curseforge.md

@@ -12,6 +12,7 @@ To manage a CurseForge modpack automatically with upgrade support, pinned or lat
     
     Example if your key is `$11$22$33aaaaaaaaaaaaaaaaaaaaaaaaaa`:
     ```yaml
+    # compose.yaml
     environment:
       CF_API_KEY: '$$11$$22$$33aaaaaaaaaaaaaaaaaaaaaaaaaa'
     ```
@@ -21,12 +22,30 @@ To manage a CurseForge modpack automatically with upgrade support, pinned or lat
     docker run ... -e CF_API_KEY='$11$22$33aaaaaaaaaaaaaaaaaaaaaaaaaa'
     ```
     
-    To avoid exposing the API key, it is highly recommended to use a `.env` file, which is [loaded automatically by docker compose](https://docs.docker.com/compose/environment-variables/set-environment-variables/#substitute-with-an-env-file). `$`'s in the value still need to escaped with a second `$` and the variable needs to be referenced from the compose file, such as:
+    To avoid exposing the API key, it is highly recommended to use a `.env` file, which is [loaded automatically by docker compose](https://docs.docker.com/compose/environment-variables/set-environment-variables/#substitute-with-an-env-file). You **do not** need to escape `$`'s with a second `$` in the `.env` file **as long as the key is wrapped in single quotes**. 
+    
+    ```
+    # .env
+    CF_API_KEY='$11$22$33aaaaaaaaaaaaaaaaaaaaaaaaaa'
+    ```
+    
+    The variable should to be referenced from the compose file, such as:
+    
     ```yaml
+    # compose.yaml
     environment:
       CF_API_KEY: ${CF_API_KEY}
     ```
     
+    The .env file should be placed in the same directory as your compose file like so:
+
+    ```
+    /minecraft-server
+    ├── .env
+    ├── compose.yaml
+    ├── /data
+    ```
+    
     To use the equivalent with `docker run` you need to specify the `.env` file explicitly:
     ```
     docker run --env-file=.env itzg/minecraft-server