Concepts Numbers and Arithmetic Operators: Improve about.md content

It would be good to check the about.md files of the concepts numbers and arithmetic-operators for possible improvements/additions. This task has a lower priority but if someone is interested in working on this, please volunteer.

For example in the about.md for numbers it would be good to make sure the special “numbers” NaN, and +/- Infinity are explained well. Also it would be good to show that/how you can write numbers with exponential and underscore notation.

Here some ideas for the about.md of arithmetic-operators:

• behavior of % if one operand is negative, see MDN docs below the demo box
• clarify difference between remainder and modulo operator in some other languages
• typical use of % for keeping a value inside a range/ “if you reach the end while iterating, start from the beginning” (not sure how to describe this well but explanation should also be understandable for someone who does not know ring theory)

The general documentation on concepts can be found here: https://exercism.org/docs/building/tracks/concepts

[SyllightTheway]

Hi, I would like to volunteer on this issue.

[junedev]

I am closing this issue, the most important parts were addressed by the PR above.