Added config to run selenium and capybara e2e tests in gitpod.

[kohheepeace]

Hi, @ghuntley

Issue

Currently, system tests by selenium cannot be run on gitpod.

This is also reported in forum https://community.gitpod.io/t/how-to-run-a-selenium-test-on-gitpod/638/6

PR

This PR added a config to run selenium and capybara system tests with :headless_chrome.

How to check this PR

Start this branch with gitpod and run the following command.

rails g scaffold Post title content
rails db:migrate
rails test:system

If you can run the system test, it is working correctly.

Refs

This code is from @thibaudgg's this repository and this PR .

I have removed some code from the above code, leaving only the minimum required settings for running system test, but I may have removed some necessary code. I am a linux newbie so I would appreciate if you could review it.

Also, the docker config file for this repository may refer to this gist.

Thanks 👍