feat: custom JSON serializer support

[mkazlauskas]

Context

If you need to support numeric values larger than Number.MAX_SAFE_INTEGER, you can't use built-in JSON.parse/JSON.stringify.

While most JSON parsers assume numeric values have same precision restrictions as IEEE 754 double, JSON specification does not say anything about number precision. Any floating point number in decimal (optionally scientific) notation is valid JSON value. It's a good idea to serialize values which might fall out of IEEE 754 integer precision as strings in your JSON api, but { "value" : 9223372036854775807}, for example, is still a valid RFC4627 JSON string, and in most JS runtimes the result of JSON.parse is this object: { value: 9223372036854776000 }

source

Proposed solution

Add a new optional option: jsonSerializer

[jasonkuhrt]

Can you write docs for this (readme):

• reference, this exists, how to use it
• guide, when you'd use it, how, why

[mkazlauskas]

Added a section in README examples. Let me know if any additional docs are needed.

[jasonkuhrt]

LGTM!