Create a webpage that allows configuration of the javascript- select a base, operands, range of numbers.
This is the complete form, now connect it to the javascript.
Take base from url parameter, also allow text characters like a-f for bases bigger than 10
Using proper base for toString.  The digit displays need to be sized to handle number of digits.
Passing in url parameters for min and max operands, add more error checking later
Fixed ambiguity with numbers, adding 0 to a number resulted in string concatenation before.
Make sure number is bigger than zero, otherwise other keys get interpretted as digit inputs.