Add workflow_dispatch to the "ci" Workflow

[tony-laza]

This is helpful when testing a PR to be able to manually run the workflow.

[yguel]

Many thanks for your contribution.
Your PR has been merged.

Side question:
We are working on using Earthly to enable users to run workflows locally, and to deploy the code on many other platform than github. Would you consider that would help you to contribute to a project like ethercat_driver_ros2 ?

[tony-laza]

Thanks for merging this. For our development, we have a GitHub fork of the repo, and we can run tests there (especially with this change so we can click the "start" button). Also, we're able to run colcon test locally + pre-commit which helps us run most of the tests locally. Being able to run the full workflow locally would help a bit, but I don't think it's a blocker for us. Another advantage to using Earthly might be to reduce dependence on GitHub itself in case there's a need to migrate the project to another hosting platform.