Improve "Try it" section in README.md

[mik-laj]

Hello,

I improved the commands that allow you to run the application:

• separated running the app and creating a variable with a Github token into two commands. This allows for easier adaptation of the example to a specific use case, e.g. using a token from CLI or copied from a website.
• mounted configuration file from local filesystem as user will probably want to test this project against their repository, but the location of this file in the container is not obvious
• added a hint using a token from Github CLI.. If user has Github CLI and Docker, user can run this project with one click 🎉

Best regards,
Kamil Breguła

[tstromberg]

Looks great!