Update core git config files, vendor installs for unit testing

Update .gitattributes with more files to ignore
Add .gitignore for php unit test cache
Install dotenv file parser for unit testing
Update current test pages with dotenv file parser (replaces function
call)

Documentation PHPdoc update for checkMe method call

src/AmazonIncentives.php

@@ -137,6 +137,10 @@ final class AmazonIncentives
 	// *********************************************************************
 
 	/**
+	 * Prints out ENV, CONFIG and KEY data
+	 * This is for debug only, this will print out secrets.
+	 * Use with care
+	 *
 	 * @return array<mixed>
 	 */
 	public function checkMe(): array