Define phantom worker tasks

We should determine what task the 'phantom workers' should have. Each task must have a description formulated in this way:
- Name of task - eg. `create_and_merge_pr`
- Description - eg. `Phantom worker creates and merges dummy PR to its own file in phantom-factory repo`
- Schedule - eg. `0,20,40 * * * *`, every 0,20,40 minute