Update README.md

Minishlink · web-flow · commit a9b689675c16 · 2020-09-13T13:07:25.000+08:00
diff --git a/README.md b/README.md
@@ -11,7 +11,7 @@ As it is standardized, you don't have to worry about what server type it relies
 ## Requirements
 
 PHP 7.2+ and the following extensions:
- * gmp
+ * gmp (optional but better for performance)
  * mbstring
  * curl
  * openssl
