[FEATURE] Supporting rational numbers

[tommens]

Describe the new functionality you would like to see
It would be useful to have primitive built-in support for rational numbers in the calculator (e.g. 3/4, 12/7, ...). A rational number can be seen as a fraction of two integer numbers.
https://en.wikipedia.org/wiki/Rational_number

Is your feature request related to a specific need or problem?
The idea of this extension is NOT to consider such fractions as decimal floating point numbers (e.g. 0.75 instead of 3/4) as this will lead to a loss of precision (e.g. 1/3 = 0.333333... but it is not possible to represent an infinite sequence of numbers in the decimal notation).
So we need arithmetic operations that work directly over rational numbers to avoid such loss of precision.

Additional context
(Some languages, such as Scheme provide built-in support for rational numbers.)