add support for js built-in data type "bigint"

[sseide]

current implementation does not support the javascript builtin data type "bigint". This type is handled like normal numbers and JSON.stringify() is called curently. After this call most big numbers does change its value as they do not fit into the "number" data range.

example with x = 66110734225681139n resp. x = BigInt(66110734225681139)

console.log( x )  ==> 66110734225681139
console.log( JSON.stringify(x) ) ==> 66110734225681140

This patch checks if data are of type bigint and displays them directly as "number" data type not calling JSON.stringify().