Add GitHub actions workflow to test building the LDWizard

[vemonet]

Hi, I created a GitHub Actions to test if the LDWizard successfully builds using the default config (yarn build) with node 14, 16, 18 and it tests building the docker image

It was requested by @GerwinBosch in https://github.com/pldn/LDWizard/issues/38, and it is really useful to check if the LDWizard properly builds on various version of NodeJS after making changes.

You can see a successful run here: https://github.com/vemonet/LDWizard/actions/runs/3932925950

I put the following triggers:

• push: will be triggered by a push to the main branch, if there is a change in the paths specified (src/, webpack/, etc mainly to avoid triggering if there is just changes to a markdown file)
• pull_request: triggered to test if LDWizard build successfully with the changes made in the pull request
• workflow_call: allow to call this workflow from another GitHub Actions workflow, really convenient if you want to also have a publish workflow that is triggered when a new release is created on GitHub (so you can run the test before publishing without duplicating the workflow code)
• workflow_dispatch: to trigger it manually, if you want to run it on a specific branch, or for some reason the workflow did not trigger, you can trigger it yourself on any branch to check if the build passes

I added a badge at the top of README.md and CONTRIBUTING.md. Not sure if you want to have it in the README, personnally I find it really convenient to have it there because it helps to quickly spot when the workflow has failed

And I changed the default webpack/runtimeConfig.ts to use a custom config with column refinement, it enables to test more features of the LDWizard when in development and tests

If you are interested we could also setup a workflow to automatically publish to npm when a release is created on GitHub. It will require to add a NPM auth token as secret (ideally one that only has access to the ldwizard package for security)

[vemonet]

No problem, I rebased the branch on main