Fix license update GH action with a cron task

[guimachiavelli]

Since MIT licenses do not support open-ended dates (e.g. 2018— is not valid, 2018-2022 is), we must update ours every year.

We have a GH action, https://github.com/FantasticFiasco/action-update-license-year/, that should do that, but at the moment it is only partially configured. To finish setting it up, we must:

• [ ] Create a proper trigger. This should probably be a cron task that runs once every january 1st;
• [ ] Update the action version: we currently use v1, but I believe there's no reason we shouldn't bump to it to the latest tagged version;
• [ ] Add a github token: it doesn't seem like the workflow will successfully run otherwise. Check with @curquiza for this, since we would ideally use a token not tied to our individual accounts

For more information on configuring the action, take a look at the examples on this repo's readme: https://github.com/FantasticFiasco/action-update-license-year/

Finally—add @curquiza as a reviewer for the PR closing this issue.