Mention cap_sys_tty_config in readme

Author: ddevault

README.md

@@ -67,6 +67,7 @@ Run these commands:
     make
     sudo make install
     sudo setcap cap_sys_ptrace=eip /usr/local/bin/sway
+    sudo setcap cap_sys_tty_config=eip /usr/local/bin/sway
 
 On systems without logind, you need to suid the sway binary: