We might want to add source polling as a trigger, as that would allow tools not to have to configure anything on their ci.

This task is to investigate how that would be feasible, and if so (and there's no big tradeoffs) then implement it.

This includes defining how to specify the triggers for your component, for example could be adding a new section to the config, something like:

...
components:
    my-component:
        build:
            repository: "https://gitlab.wikimedia.org/toolforge-repos/wm-lol"
            ref: "main"
            triggers:
              - "on-repo-changed"