String-only parsing mode

[LONGACAT]

Add an optional parameter to the parse function which makes the returned object contain only strings.

Use case - parsing an appmanifest.acf, some of the values lose precision if they're numbers. The file contains:
"manifest" "5024399731943401779"
Parsing it will return:
manifest: 5024399731943401000
A part of the value is lost. After removing the code which was responsible for converting the types, it's correctly parsed as:
manifest: '5024399731943401779'

Responsible code:

if (val !== '' && !isNaN(val)) val = +val;
if (val === 'true')            val = true;
if (val === 'false')           val = false;
if (val === 'null')            val = null;
if (val === 'undefined')       val = undefined;

[lenovouser]

@WinterNya theoretically we could also move to bigint and then no precision would be lost, but I am not sure on how to solve that cleanly

[0x3e]

I have a suggestion, allow for a passed function to do the type coercion. Keep backwards compatibility, do strings by default and then coerce. Allow the passing of a custom coercer function.

Some example functions that cover the issues I have found including @cbartondock improvements and @LONGACAT request for string only.

const functions = {
  strings: {coercer: strings => strings},
  node_steam_vdf: {},
  little_better: {
    mangle: true,
    coercer: (k, v) => {
      if (+v === Number.POSITIVE_INFINITY) v = String(v)
      else if (+v === Number.NEGATIVE_INFINITY) v = String(v)
      else if (v !== "" && !Number.isNaN(v) && String(+v) === v) v = +v
      else if (v === "true") v = true
      else if (v === "false") v = false
      else if (v === "null") v = null
      else if (v === "undefined") v = undefined

      return {k: k, v: v}
    },
  },
  cbartondock_vdf: {
    mangle: true,
    coercer: (k, val) => {
      if (val !== "" && !Number.isNaN(+val) && String(+val) === val)
        val = +val
      else if (val === "true") val = true
      else if (val === "false") val = false
      else if (val === "null") val = null
      else if (val === "undefined") val = undefined

      return {k: k, v: val}
    },
  },
}

Or users can go further and use a json schema to better coerce the types https://github.com/0x3e/vdf/blob/node-steam/vdf/issues/10/test/coerce.test.js I imagine there is a typescript way to do it as well.

I have some tests and example changes but only for javascript https://github.com/0x3e/vdf/tree/node-steam/vdf/issues/10 including a diff for the hacking together of these examples https://github.com/0x3e/vdf/blob/node-steam/vdf/issues/10/out2.patch