add events to important care events for plants

for example: pruning, trimming, health check ... etc

https://api.github.com/ammaratef45/hydroponics-garden/blob/0ac6306e1e14c8b7435f61e4a7462f1f0e9abe59/lib/model/plant_events.dart#L5

```dart

import 'package:calendar_view/calendar_view.dart';
import 'package:flutter/material.dart';
import 'package:hydroponic_garden/model/plant.dart';

// TODO: add events to important care events for plants
// for example: pruning, trimming, health check ... etc
class PlantEvents {
final Plant _plant;

PlantEvents(this._plant);

List harvestEvents() {
List res = [];
for (int i = 0;
i < _plant.harvestDate.getDayDifference(_plant.endHarvestDate);
i++) {
DateTime date = _plant.harvestDate.add(Duration(days: i));
res.add(CalendarEventData(
title: 'harvest ${_plant.description.name} - Day $i',
date: date,
endDate: date,
startTime: date,
color: Colors.green,
));
}
return res;
}
}

```