Minor suggestions

[rfay]

Thanks for creating and maintaining this add-on!

Some suggestions implemented in this PR:

• Update the tests.yml workflow to use v2 as current in ddev-addon-template
• There's no need to use vendor/bin everywhere as it's in the PATH inside ddev-webserver
• Make ddev-selenium-standalone-chrome a dependency
• Remove version from the docker-compose, as that's long obsolete and no longer used.

And.. there's no issue queue... so some issues that I can't create:

• Please enable issues on this repository
• Please put something at least a tiny bit relevant into test.bats so it actually does something like run a trivial phpunit test
• Consider using or contributing to https://github.com/MurzNN/ddev-grafana if it's useful. I'm not sure how well maintained it is.
• In the tempo and prometheus and grafana sections of your docker-compose, use expose instead of ports. Using ports means that only one DDEV project using this can run at a time.
• I recommend removing the comments from the install.yaml as they're only distracting here.