Write functional/admin/javascript tests

I fixed the .gitlab-ci.yml to enable ESLint, we are ready to work on this task.

I was able to create Functional tests (for the Admin settings at /admin/config/fluidui/adminsettings and blacklist URLs to not render the widget) and FunctionalJavascript tests to interact with the Widget and tested the "text-size" option and worked as expected. I would like to create more tests for the other panels (font, color contrast), but I think this test is good enough for now. I'd like to test the other panels in another commit. Attached screenshots below:

For some reason the Javascript tests are not working at all in the Gitlab CI jobs: https://git.drupalcode.org/project/fluidui/-/pipelines/441180

I'm using DDEV Selenium Standalone Chrome to run the tests, if you are using DDEV as your local environment, here's some instructions on how to install it in your local ddev environment: DDEV Selenium Standalone Chrome

Here's another results of the FunctionalJS tests:

Attaching the zip with the results of the JS tests just in case

This has been ready for testing now, I'll wait for some time before merging it to the 3.0.x and create a new MR for the 2.0.x branch

I merged the tests branches to 2.0.x and 3.0.x respectively, I'll update the README.md for instructions to run the JavaScript tests. I'll mark this as "Fixed" for now.

Automatically closed - issue fixed for 2 weeks with no activity.