Improved installation instructions

`curl` using the `-s` 
and added missing `sudo`

Author: Albonycal

README.md

@@ -218,8 +218,8 @@ chmod +x "$PATH_DIR/cht.sh"
 or to install it globally (for all users):
 
 ```bash
-curl https://cht.sh/:cht.sh | sudo tee /usr/local/bin/cht.sh
-chmod +x /usr/local/bin/cht.sh
+curl -s https://cht.sh/:cht.sh | sudo tee /usr/local/bin/cht.sh
+sudo chmod +x /usr/local/bin/cht.sh
 ```
 
 Note: The package "rlwrap" is a required dependency to run in shell mode. Install this using `sudo apt install rlwrap`