Create a PR to Firefox iOS when updates to lists happens

[say-yawn]

About this PR

Related to #110, since Firefox iOS is getting the SHA of shavar-prod-lists here to generate their own Tracking Protection lists to be included in the iOS binaries, the SHA should be updated whenever Firefox iOS does a new release. Since we have a Jenkins task running every 30 minutes to check for updates on shavar-prod-lists repo and publish the changes to Shavar, we can also use the task to check that the SHA of referenced in the iOS repo is the latest SHA.

Acceptance Criteria

• Task should check if the SHA on Firefox iOS is the same as the latest SHA available
• If SHA is different create a PR to update the SHA

Side Notes

Ideally we should not be creating multiple branches or PRs to their repo for a given Firefox iOS release. I think the best way to do this is by creating a single branch, let's call it shavar-list-updates, and the shavar-list-creation task can always push to that branch and the iOS team can create a PR using that branch with the latest SHA available. This will help mitigate issues with release dates changing in the Firefox iOS team which could result into updates to tracking protections lists not being applied in time.

[say-yawn]

Superseded by #172