Update xml-to-json.xsl

[Jedimark84]

Fixed an issue where negative numbers starting with a zero must be treated as a string to maintain valid JSON output.

[Jedimark84]

Given the following xml:

<?xml version="1.0" encoding="UTF-8"?>
<root>
  <test>-0123456789</test>
</root>

It produces invalid JSON:
{"root":{"test":-0123456789}}

Proposed fix will treat -0123456789 as a string and return the following valid JSON:
{"root":{"test":"-0123456789"}}