Explain how to set as login item

[MarcAnt01]

Hello, first of all thanks for this application, being new to MacOS and being used to typing really fast the key caps delay was a huge issue and your application is really helpful. I was using the terminal command before, but its main issue was having to retype it at every reboot, now I've found out that this application can be added to login-items manually, even if there is no mention of this in the Readme, if you agree I'd be happy to propose some suggestions to the readme via a pull request