Add tips for API app creation & creds warning

README.md

@@ -8,6 +8,8 @@ A Discord Rich Presence integration for [@42School](https://github.com/42School)
 2. On Linux and macOS: Run `chmod +x ./RP42`
 3. Create an API App on the Intranet: https://profile.intra.42.fr/oauth/applications/new
 
+/!\ Do NOT share your credentials to someone else, or on GitHub, etc. /!\
+
 ## Usage
 Run the app like this, using the credentials of your API App:
   - Linux: `./RP42 -i CLIENT_ID -s CLIENT_SECRET &`  

cmd/RP42/main.go

@@ -141,8 +141,12 @@ func onReady() {
 	flag.StringVar(&apiSecret, "secret", "", "Client Secret from API settings")
 	flag.Usage = func() {
 		fmt.Print(`Usage of RP42:
-	-i, --id Client ID from API settings (required)
-	-s, --secret Client Secret from API settings (required)
+	-i, --id Client ID of your API app (required)
+	-s, --secret Client Secret of your API app (required)
+	
+If you don't have an API app yet, create one here: https://profile.intra.42.fr/oauth/applications/new
+/!\ Do NOT share your credentials to someone else, or on GitHub, etc. /!\
+
 `)
 	}
 	flag.Parse()