Documentation about how to set up self-hosted runners

[LastStarDust]

First of all thank you for developing such a useful action.

It works flawlessly for github runners but I am having trouble for a non ephemeral self-hosted runner.

By reading some issues, I came to understand that self-hosted runners need some manual configuration, like setting up the known hosts file and such.

While I could figure it out on my own with some effort, it would be much appreciated if the README file explained the steps needed to set up self-hosted runners.

[chufnagel]

Seconded, also experiencing issues with non-ephemeral self-hosted runners. @LastStarDust what manual configuration did you need to perform if you're able to share?

[LastStarDust]

I had to reset the SSH and git configuration of the self-hosted runner and then I had to manually copy the private SSH keys with appropriate names. Moreover I had to modify the following snippet with the correct user name of the runner.

RUN sed 's|/home/runner|/root|g' -i.bak /root/.ssh/config