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