Create 3 functions that works like the `.filter`, `.map` and `.reduce` array method but for the entries of the grocery cart.
- `filterEntries` filters using both key and value.
- `mapEntries` changes either the key or the value or both.
- `reduceEntries` reduce over entries.
Create 3 other functions that use your previously create functions:
- `totalCalories` that will return the total calories of a cart
- `lowCarbs` that will leave only items that total carbs are lower than 50grams
- `cartTotal` that will give you the right amount of calories, proteins, ..., of all items in your grocery cart.
### Clarification
What the functions will take as argument is an object cart which contains the food rations. All the nutrition in the nutritionDB object are measured per 100 grams.
