Capslock (and other keys) indicator for Ubuntu 18.04

You may use one of the following GNOME shell extensions to achieve your goal.

• Lock Keys
  This extension shows Num lock or Caps lock (or both) status on the top bar.
  

• Keys Indicator
  This extension shows Ctrl, Shift, Alt, Num lock, and Caps lock status on the top bar.
  

• Lock Keys (another one)
  Numlock & Capslock status on the panel. Icons are auto hidden. Simplified with no menus, notifications or settings.

There's a ppa for indicator-keylock on Ubuntu 18.04

sudo add-apt-repository ppa:tsbarnes/indicator-keylock
sudo apt-get update
sudo apt-get install indicator-keylock