Addition of between?/3 to Calendar module

[edward omondi]

I have been extensively working with dates recently and found the need to create a function between?/3. This function takes first_date, second_date, and target_date as inputs and returns a boolean indicating whether target_date is between first_date and second_date, inclusive of the boundaries if specified.

While the Timex library offers this functionality, the recently added Calendar module in Elixir already provides most of the features I need, except for this specific function. I believe it would be beneficial to include this functionality in the Calendar module.

Proposal

Function: Calendar.between?/3

Description: This function checks if target_date falls between first_date and second_date. By default, the boundaries are exclusive. An optional keyword list allows the inclusion of boundaries.

Example Usage:

```elixir

Calendar.between?(datetime_1, datetime_2, datetime_3)

```

Returns true if datetime_3 is between datetime_1 and datetime_2, exclusive of datetime_1 and datetime_2.

```elixir

Calendar.between?(datetime_1, datetime_2, datetime_3, inclusive: true)

```

Of course, there are other factors to consider, but setting aside the implementation details, what is the feasibility of adding this function?