README: adds comments

Author: CarterLi

README.md

@@ -15,6 +15,8 @@
 
 Fastfetch is a [neofetch](https://github.com/dylanaraps/neofetch)-like tool for fetching system information and displaying it in a visually appealing way. It is written mainly in C, with a focus on performance and customizability. Currently, it supports Linux, macOS, Windows 8.1+, Android, FreeBSD, OpenBSD, NetBSD, DragonFly, Haiku and SunOS (illumos, Solaris).
 
+> Note: Fastfetch is only actively tested on x86-64 and aarch64 platforms. It may work on other platforms but is not guaranteed to do so.
+
 <img src="screenshots/example1.png" width="49%" align="left" />
 <img src="https://upload.wikimedia.org/wikipedia/commons/2/24/Transparent_Square_Tiles_Texture.png" width="49%" height="16px" align="left" />
 <img src="screenshots/example4.png" width="49%" align="left" />