Add --check to troubleshooting docs

doc/articles/troubleshooting.md

@@ -10,7 +10,10 @@ This is a list of common pitfalls on using Composer, and how to avoid them.
 1. When facing any kind of problems using Composer, be sure to **work with the
    latest version**. See [self-update](../03-cli.md#self-update) for details.
 
-2. Ensure you're **installing vendors straight from your `composer.json`** via
+2. Make sure you have no problems with your setup by running the installer's
+   checks via `curl -s https://getcomposer.org/installer | php -- --check`.
+
+3. Ensure you're **installing vendors straight from your `composer.json`** via
    `rm -rf vendor && composer update -v` when troubleshooting, excluding any
    possible interferences with existing vendor installations or `composer.lock`
    entries.