Improved config description

static/defaults.config.php

@@ -442,7 +442,8 @@ return [
 		'no_smilies' => false,
 
 		// tesseract_ocr (Boolean)
-		// Use Tesseract OCR to use OCR to fetch text from images
+		// Use Tesseract OCR to use OCR to fetch text from images.
+		// The Tesseract OCR command line tool needs to be installed separately on the system.
 		'tesseract_ocr' => false,
 
 		// optimize_all_tables (Boolean)