question 8: forbid strings, add grid background and randomize question matrix values

[x] Randomization for task cube.
[✗] randomization of starting matrix values for default user controlled cube is not really needed. Although its the exact same procedure as for randomization for task cube matrix.
[✗] add grid background , debatable if it is better with or without

after some thought, there is pretty much no reason to restrict the user from inputing strings. If STACK does not have a validation method of check if the input is string, then no need to use JavaScript because restricting input is annoying for users.

IDIAMath / idiamath.github.io

question 8: forbid strings, add grid background and randomize question matrix values #64