Run ohw bump image tags workflow more frequently

[GeorgianaElena]

Adds a new workflow to bump ohw image tags more frequently.

The current bump-image-tags workflow runs once every week, so this temporarily adds a new workflow that runs every 6 hours and checks for new image tags for the ohw hub. We should keep this probably only during the event #1576.

I chose 6h as the interval since this means 4 times a day and it means about two times during someone's awake time. But feel free to suggest another value if it makes more sense.

TODO:

• add removing this workflow on the todo list of the issue tracking the event once this PR is accepted
• add this as a suggested practice in the event issue template for hubs that run multiple images per user profile and hence the configurator doesn't work for them. -> Automate updating user images in profile list - temporary solution #1590

[sgibson91]

Looks good to me!

In the future, we could have an events workflow that has a matrix similar to the current workflow so we can easily add/remove entries as we need them maybe? Probably need to test this practice out for a few events before deciding if that's a real need or not.