Ability to add, hide and rename lessons

[yerlotic]

I would like to see this implemented because:

• some titles of various subjects are strange and should've been smaller
• it would easier to track afterschool activities that are not in schedule
• what's wrong with having fun messing around with lesson's name?

From ui/ux perspective:

1. you tap and hold on a lesson in "Schedule" tab
2. the popup with lesson's name (editable), checkbox to hide this lesson (for all days on the specific weekday of this lesson) and a save button at the bottom that hides this ui and shows the updated schedule.

Also at the botton of schedule tab there is a wide button to add new lesson with given name. Time, duration and teacher are optional fields. If time has'n been provided, this lesson should be displayed at the bottom.

The popup should have a button to edit or delete lesson if it has been manually created (not from api.mos.ru)

Possible way to implement:

The info about changes to the scedule could be stored in json (or similar) file that contains only the changes to the schedule.
Something like this:

{
  "monday": {
    "changes": {
      "10:30-11:15": {
        "name": "new name🔥",
        "isHidden": false,
        "teacher": "new name for teacher"
                      }
                },
    "new": [
      {"name": "soccer"},
      {"name": "basketball", "teacher": "idk", "start": "18:45", "duration (minutes)": 45}
            ]
             }
}