update README

diff --git a/README.md b/README.md
index dfdb63a493b054396501d7a847cf282dd8896c6a..a919e47f4e93835582e7cb7c07a2ec34db8084e2 100644 (file)
--- a/README.md
+++ b/README.md
@@ -11,7 +11,8 @@ ttyd is a simple command-line tool for sharing terminal over the web.
 - Built on top of [Libwebsockets](https://libwebsockets.org) with [libuv](https://libuv.org) for speed
 - Fully-featured terminal based on [Xterm.js](https://xtermjs.org) with [CJK](https://en.wikipedia.org/wiki/CJK_characters) and IME support
 - Graphical [ZMODEM](https://en.wikipedia.org/wiki/ZMODEM) integration with [lrzsz](https://ohse.de/uwe/software/lrzsz.html) support
-- SSL support based on [OpenSSL](https://www.openssl.org)
+- [Sixel](https://en.wikipedia.org/wiki/Sixel) image output support ([Usage](https://saitoha.github.io/libsixel/))
+- SSL support based on [OpenSSL](https://www.openssl.org) / [Mbed TLS](https://github.com/Mbed-TLS/mbedtls)
 - Run any custom command with options
 - Basic authentication support and many other custom options
 - Cross platform: macOS, Linux, FreeBSD/OpenBSD, [OpenWrt](https://openwrt.org), Windows