Support function to transform xml using xsl transformation

[rohitjangid]

We should support a function to convert a stringified xml using stringified xsl. The details could be as follows

• Signature: std.xsltTransform(xml, xsl)
• Params:
  1. xml: XML string
  2. xsl: XSL string
• Returns: Stringified transformed output

Ref: https://en.wikipedia.org/wiki/XSLT

[rohitjangid]

@sparkprime Do you have any suggestion wrt this? Specifically regarding function signature?