Chrome has to be run at least once before mkcert notices it

[JasonBarnabe]

If Chrome is installed but has never been run, mkcert -install doesn't install the CA to its trust store. Not really an issue on a desktop, but I was trying to get mkcert running in a CircleCI build and ran into it. If it can't be fixed, it should at least be documented:

Workaround (for CircleCI): start Chrome and kill it before running mkcert -install.

      - run:
          name: Start Chrome so that mkcert sees it
          command: |
            /opt/google/chrome/google-chrome &
            sleep 3
            killall chrome

[JasonBarnabe]

This is the same as #219, and that has a better workaround.